MNC php interview questions and answers

1) what is session_set_save_handler in PHP? session_set_save_handler() sets the user-level session storage functions which are used for storing and retrieving data associated with a session. This is most useful when a storage method other than those supplied by PHP sessions is preferred. i.e. Storing the session data in a local database.

2) what is garbage collection? default time ? refresh time? Garbage Collection is an automated part of PHP , If the Garbage Collection process runs, it then analyzes any files in the /tmp for any session files that have not been accessed in a certain amount of time and physically deletes them. arbage Collection process only runs in the default session save directory, which is /tmp. If you opt to save your sessions in a different directory, the Garbage Collection process will ignore it. the Garbage Collection process does not differentiate between which sessions belong to whom when run. This is especially important note on shared web servers. If the process is run, it deletes ALL files that have not been accessed in the directory.

There are 3 PHP.ini variables, which deal with the garbage collector: PHP ini  value

name                                          default

session.gc_maxlifetime     1440 seconds or 24 minutes

session.gc_probability      1

session.gc_divisor              100

3) PHP how to know user has read the email? Using Disposition-Notification-To: in mailheader we can get read receipt.

Add the possibility to define a read receipt when sending an email.

It’s quite straightforward, just edit email.php, and add this at vars definitions:

var $readReceipt = null;

And then, at ‘createHeader’ function add:

if (!empty($this->readReceipt)) { $this->__header .= ‘Disposition-Notification-To: ‘ . $this->__formatAddress($this->readReceipt) . $this->_newLine; }

4) Runtime library loading ? without default mysql support, how to run mysql with php?

dl — Loads a PHP extension at runtime int dl ( string $library )

Loads the PHP extension given by the parameter library .

Use extension_loaded() to test whether a given extension is already available or not. This works on both built-in extensions and dynamically loaded ones (either through php.ini or dl()).

bool extension_loaded ( string $name ) — Find out whether an extension is loaded

Warning :This function has been removed from some SAPI’s in PHP 5.3.

5) what is XML-RPC ? XML-RPC is a remote procedure call protocol which uses XML to encode its calls and HTTP as a transport mechanism. An XML-RPC message is an HTTP-POST request. The body of the request is in XML. A procedure executes on the server and the value it returns is also formatted in XML.

6) default session time ? default session time in PHP is 1440 seconds or 24 minutes.

7) default session save path ? Default session save path id temporary folder /tmp

8) What is the difference between htmlentities() and htmlspecialchars()?

htmlspecialchars() – Convert some special characters to HTML entities (Only the most widely used) htmlentities() – Convert ALL special characters to HTML entities

9) how to do session using DB?

bool session_set_save_handler ( callback $open , callback $close , callback $read , callback $write , callback $destroy , callback $gc ) using this function we can store sessions in DB.

PHP has a built-in ability to override its default session handling. The function session_set_save_handler() lets the programmer specify which functions should actually be called when it is time to read or write session information. by overriding the default functions using session_set_save_handler handle we can store session in Db like below example

class SessionManager {

var $life_time;

function SessionManager() {

// Read the maxlifetime setting from PHP $this->life_time = get_cfg_var(“session.gc_maxlifetime”);

// Register this object as the session handler session_set_save_handler( array( &$this, “open” ), array( &$this, “close” ), array( &$this, “read” ), array( &$this, “write”), array( &$this, “destroy”), array( &$this, “gc” ) );

}

function open( $save_path, $session_name ) {

global $sess_save_path;

$sess_save_path = $save_path;

// Don’t need to do anything. Just return TRUE.

return true;

}

function close() {

return true;

}

function read( $id ) {

// Set empty result $data = ”;

// Fetch session data from the selected database

$time = time();

$newid = mysql_real_escape_string($id); $sql = “SELECT `session_data` FROM `sessions` WHERE `session_id` = ‘$newid’ AND `expires` > $time”;

$rs = db_query($sql); $a = db_num_rows($rs);

if($a > 0) { $row = db_fetch_assoc($rs); $data = $row[‘session_data’];

}

return $data;

}

function write( $id, $data ) {

// Build query $time = time() + $this->life_time;

$newid = mysql_real_escape_string($id); $newdata = mysql_real_escape_string($data);

$sql = “REPLACE `sessions` (`session_id`,`session_data`,`expires`) VALUES(‘$newid’, ‘$newdata’, $time)”;

$rs = db_query($sql);

return TRUE;

}

function destroy( $id ) {

// Build query $newid = mysql_real_escape_string($id); $sql = “DELETE FROM `sessions` WHERE `session_id` = ‘$newid'”;

db_query($sql);

return TRUE;

}

function gc() {

// Garbage Collection

// Build DELETE query. Delete all records who have passed the expiration time $sql = ‘DELETE FROM `sessions` WHERE `expires` < UNIX_TIMESTAMP();’;

db_query($sql);

// Always return TRUE return true;

}

}

10) how to track user logged out or not? when user is idle ? By checking the session variable exist or not while loading th page. As the session will exist longer as till browser closes.

The default behaviour for sessions is to keep a session open indefinitely and only to expire a session when the browser is closed. This behaviour can be changed in the php.ini file by altering the line session.cookie_lifetime = 0 to a value in seconds. If you wanted the session to finish in 5 minutes you would set this to session.cookie_lifetime = 300 and restart your httpd server.

11) how to track no of user logged in ? whenever a user logs in track the IP, userID etc..and store it in a DB with a active flag while log out or sesion expire make it inactive. At any time by counting the no: of active records we can get the no: of visitors.

12) in PHP for pdf which library used?

The PDF functions in PHP can create PDF files using the PDFlib library With version 6, PDFlib offers an object-oriented API for PHP 5 in addition to the function-oriented API for PHP 4. There is also the » Panda module.

FPDF is a PHP class which allows to generate PDF files with pure PHP, that is to say without using the PDFlib library. F from FPDF stands for Free: you may use it for any kind of usage and modify it to suit your needs.

FPDF requires no extension (except zlib to activate compression and GD for GIF support) and works with PHP4 and PHP5.

13) for image work which library?

You will need to compile PHP with the GD library of image functions for this to work. GD and PHP may also require other libraries, depending on which image formats you want to work with.

14) what is oops? encapsulation? abstract class? interface?

Object oriented programming language allows concepts such as modularity, encapsulation, polymorphism and inheritance.

Encapsulation passes the message without revealing the exact functional details of the class. It allows only the relevant information to the user without revealing the functional mechanism through which a particular class had functioned.

Abstract class is a template class that contains such things as variable declarations and methods, but cannot contain code for creating new instances. A class that contains one or more methods that are declared but not implemented and defined as abstract. Abstract class: abstract classes are the class where one or more methods are abstract but not necessarily all method has to be abstract. Abstract methods are the methods, which are declare in its class but not define. The definition of those methods must be in its extending class.

Interface: Interfaces are one type of class where all the methods are abstract. That means all the methods only declared but not defined. All the methods must be define by its implemented class.

15) what is design pattern? singleton pattern?

A design pattern is a general reusable solution to a commonly occurring problem in software design.

The Singleton design pattern allows many parts of a program to share a single resource without having to work out the details of the sharing themselves.

16) what are magic methods?

Magic methods are the members functions that is available to all the instance of class Magic methods always starts with “__”. Eg. __construct All magic methods needs to be declared as public To use magic method they should be defined within the class or program scope Various Magic Methods used in PHP 5 are: __construct() __destruct() __set() __get() __call() __toString() __sleep() __wakeup() __isset() __unset() __autoload() __clone()

17) what is magic quotes? Magic Quotes is a process that automagically escapes incoming data to the PHP script. It’s preferred to code with magic quotes off and to instead escape the data at runtime, as needed. This feature has been DEPRECATED as of PHP 5.3.0 and REMOVED as of PHP 6.0.0. Relying on this feature is highly discouraged.

18) diff b/w php4 & php5 ? In PHP5 1 Implementation of exceptions and exception handling

2. Type hinting which allows you to force the type of a specific argument as object, array or NULL

3. Overloading of methods through the __call function

4. Full constructors and destructors etc through a __constuctor and __destructor function

5. __autoload function for dynamically including certain include files depending on the class you are trying to create.

6 Finality : can now use the final keyword to indicate that a method cannot be overridden by a child. You can also declare an entire class as final which prevents it from having any children at all.

7 Interfaces & Abstract Classes

8 Passed by Reference : In PHP4, everything was passed by value, including objects. This has changed in PHP5 — all objects are now passed by reference.

9 An __clone method if you really want to duplicate an object

19) in php4 can you define a class? how to call class in php4? can you create object in php4?

yes you can define class and can call class by creating object of that class. but the diff b/w php4 & php5 is that in php4 everything was passed by value where as in php5 its by reference. And also any value change in reference object changes the actucal value of object also. And one more thing in introduction of __clone object in PHP5 for copying the object.

20) types of error? how to set error settings at run time?

here are three basic types of runtime errors in PHP:

1. Notices: These are trivial, non-critical errors that PHP encounters while executing a script – for example, accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all – although you can change this default behaviour.

2. Warnings: These are more serious errors – for example, attempting to include() a file which does not exist. By default, these errors are displayed to the user, but they do not result in script termination.

3. Fatal errors: These are critical errors – for example, instantiating an object of a non-existent class, or calling a non-existent function. These errors cause the immediate termination of the script, and PHP?s default behaviour is to display them to the user when they take place.

by using ini_set function.

21) what is cross site scripting? SQL injection?

Cross-site scripting (XSS) is a type of computer security vulnerability typically found in web applications which allow code injection by malicious web users into the web pages viewed by other users. Examples of such code include HTML code and client-side scripts.

SQL injection is a code injection technique that exploits a security vulnerability occurring in the database layer of an application. The vulnerability is present when user input is either incorrectly filtered for string literal escape characters embedded in SQL statements or user input is not strongly typed and thereby unexpectedly executed

22) what is outerjoin? inner join?

OUTER JOIN in SQL allows us to retrieve all values in a certain table regardless of whether these values are present in other tables

An inner join requires each record in the two joined tables to have a matching record. An inner join essentially combines the records from two tables (A and B) based on a given join-predicate.

23) what is URL rewriting?

Using URL rewriting we can convert dynamic URl to static URL Static URLs are known to be better than Dynamic URLs because of a number of reasons 1. Static URLs typically Rank better in Search Engines. 2. Search Engines are known to index the content of dynamic pages a lot slower compared to static pages. 3. Static URLs are always more friendlier looking to the End Users.

along with this we can use URL rewriting in adding variables [cookies] to the URL to handle the sessions.

24) what is the major php security hole? how to avoid?

1. Never include, require, or otherwise open a file with a filename based on user input, without thoroughly checking it first. 2. Be careful with eval() Placing user-inputted values into the eval() function can be extremely dangerous. You essentially give the malicious user the ability to execute any command he or she wishes! 3. Be careful when using register_globals = ON It was originally designed to make programming in PHP easier (and that it did), but misuse of it often led to security holes 4. Never run unescaped queries 5. For protected areas, use sessions or validate the login every time. 6. If you don’t want the file contents to be seen, give the file a .php extension.

25) whether PHP supports Microsoft SQL server ? The SQL Server Driver for PHP v1.0 is designed to enable reliable, scalable integration with SQL Server for PHP applications deployed on the Windows platform. The Driver for PHP is a PHP 5 extension that allows the reading and writing of SQL Server data from within PHP scripts. using MSSQL or ODBC modules we can access Microsoft SQL server.

26) what is MVC? why its been used? Model-view-controller (MVC) is an architectural pattern used in software engineering. Successful use of the pattern isolates business logic from user interface considerations, resulting in an application where it is easier to modify either the visual appearance of the application or the underlying business rules without affecting the other. In MVC, the model represents the information (the data) of the application; the view corresponds to elements of the user interface such as text, checkbox items, and so forth; and the controller manages the communication of data and the business rules used to manipulate the data to and from the model.

WHY ITS NEEDED IS 1 Modular separation of function 2 Easier to maintain 3 View-Controller separation means:

A — Tweaking design (HTML) without altering code B — Web design staff can modify UI without understanding code

27) what is framework? how it works? what is advantage?

In general, a framework is a real or conceptual structure intended to serve as a support or guide for the building of something that expands the structure into something useful. Advantages : Consistent Programming Model Direct Support for Security Simplified Development Efforts Easy Application Deployment and Maintenance

28) what is CURL?

CURL means Client URL Library

curl is a command line tool for transferring files with URL syntax, supporting FTP, FTPS, HTTP, HTTPS, SCP, SFTP, TFTP, TELNET, DICT, LDAP, LDAPS and FILE. curl supports SSL certificates, HTTP POST, HTTP PUT, FTP uploading, HTTP form based upload, proxies, cookies, user+password authentication (Basic, Digest, NTLM, Negotiate, kerberos…), file transfer resume, proxy tunneling and a busload of other useful tricks.

CURL allows you to connect and communicate to many different types of servers with many different types of protocols. libcurl currently supports the http, https, ftp, gopher, telnet, dict, file, and ldap protocols. libcurl also supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading (this can also be done with PHP’s ftp extension), HTTP form based upload, proxies, cookies, and user+password authentication.

29) HOW we can transfer files from one server to another server without web forms?

using CURL we can transfer files from one server to another server. ex:

Uploading file

<?php

/* http://localhost/upload.php: print_r($_POST); print_r($_FILES); */

$ch = curl_init();

$data = array(‘name’ => ‘Foo’, ‘file’ => ‘@/home/user/test.png’);

curl_setopt($ch, CURLOPT_URL, ‘http://localhost/upload.php&#8217;);

curl_setopt($ch, CURLOPT_POST, 1); curl_setopt($ch, CURLOPT_POSTFIELDS, $data);

curl_exec($ch); ?>

output:

Array ( [name] => Foo ) Array ( [file] => Array ( [name] => test.png
[type] => image/png [tmp_name] => /tmp/phpcpjNeQ [error] => 0 [size] => 279 )   )  

  30) using CSS can we have a scroll to table? 
No table won't support scrolling of its data. but we can do another workaround like placing a table
 in a DIV  layer and setting the DIV css property to overflow:auto will do the trick.  

  31) how to increase session time in PHP ? 
In php.ini by setting session.gc_maxlifetime and session.cookie_lifetime values
we can change the session time in PHP.   

 32) what is UI? What are the five primary user-interface components?  
 A user interface is a means for human beings to interact with computer-based "tools" and"messages".
One presumed goal is to make the user's experience productive, efficient, pleasing, and humane.
 The primary components of UIs are  a) metaphors (fundamental concepts communicated
 through words, images, sounds, etc.)

b) mental models (structure of data, functions, tasks, roles, jobs, and people in organizations of work
and/or play)
 c) navigation (the process of moving through the mental models)
d) interaction (all input-output sequences and means for conveying feedback)
 e) and appearance (visual, verbal, acoustic, etc.).

33) How can I set a cron and how can I execute it in Unix, Linux, and windows?

Cron is very simply a Linux module that allows you to run commands at predetermined times or intervals.

In Windows, it’s called Scheduled Tasks. The name Cron is in fact derived from the same word from which we get the word chronology, which means order of time.

The easiest way to use crontab is via the crontab command. # crontab This command ‘edits’ the crontab.

Upon employing this command, you will be able to enter the commands that you wish to run.

My version of Linux uses the text editor vi. You can find information on using vi here.

The syntax of this file is very important – if you get it wrong, your crontab will not function properly.

The syntax of the file should be as follows: minutes hours day_of_month month day_of_week command All the variables, with the exception of the command itself, are numerical constants.

In addition to an asterisk (*), which is a wildcard that allows any value, the ranges permitted for each field are as follows: Minutes: 0-59 Hours: 0-23 Day_of_month: 1-31 Month: 1-12 Weekday: 0-6 We can also include multiple values for each entry, simply by separating each value with a comma.

command can be any shell command and, as we will see momentarily, can also be used to execute a Web document such as a PHP file. So, if we want to run a script every Tuesday morning at 8:15 AM, our mycronjob file will contain the following content on a single line: 15 8 * * 2 /path/to/scriptname This all seems simple enough, right? Not so fast! If you try to run a PHP script in this manner, nothing will happen (barring very special configurations that have PHP compiled as an executable, as opposed to an Apache module).

The reason is that, in order for PHP to be parsed, it needs to be passed through Apache. In other words, the page needs to be called via a browser or other means of retrieving Web content.

For our purposes, I’ll assume that your server configuration includes wget, as is the case with most default configurations. To test your configuration, log in to shell.

If you’re using an RPM-based system (e.g. Redhat or Mandrake), type the following: # wget help If you are greeted with a wget package identification, it is installed in your system.

You could execute the PHP by invoking wget on the URL to the page, like so: # wget http://www.example.com/file.php Now, let’s go back to the mailstock.php file we created in the first part of this article.

We saved it in our document root, so it should be accessible via the Internet. Remember that we wanted it to run at 4PM Eastern time, and send you your precious closing bell report? Since I’m located in the Eastern timezone, we can go ahead and set up our crontab to use 4:00, but if you live elsewhere, you might have to compensate for the time difference when setting this value.

This is what my crontab will look like: 0 4 * * 1,2,3,4,5 wget http://www.example.com/mailstock.php

34)Difference b/w OOPS concept in php4 and PHP5 ?

version 4’s object-oriented functionality was rather hobbled. Although the very basic premises of objectoriented programming (OOP) were offered in version 4, several deficiencies existed, including: • An unorthodox object-referencing methodology • No means for setting the scope (public, private, protected, abstract) of fields and methods • No standard convention for naming constructors • Absence of object destructors • Lack of an object-cloning feature • Lack of support for interfaces

35) Difference b/w MyISAM and InnoDB in MySQL?

Ans:

The big difference between MySQL Table Type MyISAM and InnoDB is that InnoDB supports transaction

InnoDB supports some newer features: Transactions, row-level locking, foreign keys

InnoDB is for high volume, high performance

use MyISAM if they need speed and InnoDB for data integrity.

InnoDB has been designed for maximum performance when processing large data volumes

Even though MyISAM is faster than InnoDB

InnoDB supports transaction. You can commit and rollback with InnoDB but with MyISAM once you issue a command it’s done

MyISAM does not support foreign keys where as InnoDB supports

Fully integrated with MySQL Server, the InnoDB storage engine maintains its own buffer pool for caching data and indexes in main memory. InnoDB stores its tables and indexes in a tablespace, which may consist of several files (or raw disk partitions). This is different from, for example, MyISAM tables where each table is stored using separate files. InnoDB tables can be of any size even on operating systems where file size is limited to 2GB.

36) how to set session tiem out at run time or how to extend the session timeout at runtime?

Ans:

Sometimes it is necessary to set the default timeout period for PHP. To find out what the default (file-based-sessions) session timeout value on the server is you can view it through a ini_get command:

// Get the current Session Timeout Value
$currentTimeoutInSecs = ini_get(’session.gc_maxlifetime’);

Change the Session Timeout Value

// Change the session timeout value to 30 minutes
ini_set(’session.gc_maxlifetime’, 30*60);

If you have changed the sessions to be placed inside a Database occasionally implementations will specify the expiry manually. You may need to check through the session management class and see if it is getting the session timeout value from the ini configuration or through a method parameter (with default). It may require a little hunting about.

PHP interview questions & ANSWERS

Q:1 What are the differences between Get and post methods in form submitting.
give the case where we can use get and we can use post methods?
A:1
When to use GET or  POST

The HTML 2.0 specification says, in section Form
Submission (and the HTML 4.0 specification repeats this with minor
stylistic changes):

–>If the processing of a form is idempotent
(i.e. it has no lasting observable effect on the state of the
world), then the form method should be GET. Many database searches
have no visible side-effects and make ideal applications of query
forms.
–
–>If the service associated with the processing of a form has side
effects (for example, modification of a database or subscription to
a service), the method should be POST.
How the form data is transmitted?

quotation from the HTML 4.0 specification

–> If the method is “get” – -, the user agent
takes the value of action, appends a ? to it, then appends the form
data set, encoded using the application/x-www-form-urlencoded
content type. The user agent then traverses the link to this URI. In
this scenario, form data are restricted to ASCII codes.
–> If the method is “post” –, the user agent conducts an HTTP post
transaction using the value of the action attribute and a message
created according to the content type specified by the enctype
attribute.
Quote from CGI FAQ

Firstly, the the HTTP protocol specifies
differing usages for the two methods. GET requests should always be
idempotent on the server. This means that whereas one GET request
might (rarely) change some state on the Server, two or more
identical requests will have no further effect.

This is a theoretical point which is also good
advice in practice. If a user hits “reload” on his/her browser, an
identical request will be sent to the server, potentially resulting
in two identical database or
guestbook entries, counter increments, etc. Browsers may reload a
GET URL automatically, particularly if cacheing is disabled (as is
usually the case with CGI output), but will typically prompt the
user before
re-submitting a POST request. This means you’re far less likely to
get inadvertently-repeated entries from POST.

GET is (in theory) the preferred method for
idempotent operations, such as querying a database, though it
matters little if you’re using a form. There is a further practical
constraint that many systems have built-in limits to the length of a
GET request they can handle: when the total size of a request (URL+params)
approaches or exceeds 1Kb, you are well-advised to use POST in any
case.

I would prefer POST when I don’t want the status to
be change when user resubmits. And GET
when it does not matter.

Q:2 Who is the father of PHP and explain the changes in PHP versions?
A:2 Rasmus Lerdorf is known as the father of PHP.PHP/FI 2.0 is an early and no longer supported version of PHP. PHP 3
is the successor to PHP/FI 2.0 and is a lot nicer. PHP 4 is the current
generation of PHP, which uses the
Zend engine
under the
hood. PHP 5 uses
Zend engine 2 which,
among other things, offers many additionalOOP features

Q:3 How can we submit a form without a submit button?
A:3 The main idea behind this is to use Java script submit() function in
order to submit the form without explicitly clicking any submit button.
You can attach the document.formname.submit() method to onclick,
onchange events of different inputs and perform the form submission. you
can even built a timer function where you can automatically submit the
form after xx seconds once the loading is done (can be seen in online
test sites).

Q:4 In how many ways we can retrieve the data in the result set of
MySQL using PHP?
A:4 You can do it by 4 Ways1. mysql_fetch_row.
2. mysql_fetch_array
3. mysql_fetch_object
4. mysql_fetch_assoc

Q:5 What is the difference between mysql_fetch_object and
mysql_fetch_array?
A:5 mysql_fetch_object() is similar tomysql_fetch_array(), with one difference –
an object is returned, instead of an array. Indirectly, that means that
you can only access the data by the field names, and not by their
offsets (numbers are illegal property names).

Q:6 What is the difference between $message and $$message?
A:6 It is a classic example of PHP’s variable variables. take the
following example.$message = “Mizan”;$$message = “is a moderator of PHPXperts.”;$message is a simple PHP variable that we are used to. But the
$$message is not a very familiar face. It creates a variable name $mizan
with the value “is a moderator of PHPXperts.” assigned. break it like
this${$message} => $mizanSometimes it is convenient to be able to have variable variable
names. That is, a variable name which can be set and used dynamically.

Q:7 How can we extract string ‘abc.com ‘ from a string ‘http://info@abc.com’
using regular expression of PHP?
A:7 preg_match(”/^http:\/\/.+@(.+)$/”,’http://info@abc.com’,$found);
echo $found[1];

Q:8 How can we create a database using PHP and MySQL?
A:8 We can create MySQL database with the use of
mysql_create_db(“Database Name”)

Q:9 What are the differences between require and include,
include_once and require_once?
A:9

The include() statement includes
and evaluates the specified file.The documentation below also applies to
require(). The two constructs
are identical in every way except how they handle
failure. include() produces a
Warning while require() results
in a Fatal Error. In other words, use
require() if you want a missing
file to halt processing of the page.
include() does not behave this way, the script will
continue regardless.

The include_once()
statement includes and evaluates the
specified file during the execution of
the script. This is a behavior similar
to the include()
statement, with the only difference
being that if the code from a file has
already been included, it will not be
included again. As the name suggests, it
will be included just once.include_once()
should be used in cases where the same
file might be included and evaluated
more than once during a particular
execution of a script, and you want to
be sure that it is included exactly once
to avoid problems with function
redefinitions, variable value
reassignments, etc.

require_once()
should be used in cases where the same
file might be included and evaluated
more than once during a particular
execution of a script, and you want to
be sure that it is included exactly once
to avoid problems with function
redefinitions, variable value
reassignments, etc.

Q:10 Can we use include (”abc.PHP”) two times in a PHP page “makeit.PHP”?
A:10 Yes we can use include() more than one time in any page though it is
not a very good practice.

Q:11 What are the different tables present in MySQL, which type of
table is generated when we are creating a table in the following syntax:
create table employee (eno int(2),ename varchar(10)) ?
A:11 Total 5 types of tables we can create
1. MyISAM
2. Heap
3. Merge
4. INNO DB
5. ISAM
MyISAM is the default storage engine as of MySQL 3.23 and as a result if
we do not specify the table name explicitly it will be assigned to the
default engine.

Q:12 Functions in IMAP, POP3 AND LDAP?
A:12 These functions enable you to operate with the IMAP protocol, as well as the NNTP, POP3 and local mailbox access methods  You can find these specific information in PHP Manual.

Q:13 How can I execute a PHP script using command line?
A:13 As of version 4.3.0, PHP supports a new SAPI type (Server
Application Programming Interface) named CLI which means Command Line
Interface. Just run the PHP CLI (Command Line Interface) program and
provide the PHP script file name as the command line argument. For
example, “php myScript.php”, assuming “php” is the command to invoke the
CLI program.
Be aware that if your PHP script was written for the Web CGI interface,
it may not execute properly in command line environment.

Q:14 Suppose your Zend engine supports the mode Then how can u
configure your PHP Zend engine to support mode ?
A:14 In php.ini file:
set
short_open_tag=on
to make PHP support

Q:15 Shopping cart online validation i.e. how can we configure Paypal,
etc.?
A:15 We can find the detail documentation about different paypal
integration process at the following site

PayPal PHP
SDK : http://www.paypaldev.org

Q:16 What is meant by nl2br()?
A:16 Inserts HTML line breaks (
) before all newlines in a string
string nl2br (string); Returns string with ” inserted before all
newlines. For example: echo nl2br(”god bless\n you”) will output “god
bless
you” to your browser.

Q:17 Draw the architecture of Zend engine?
A:17 The Zend Engine is the internal compiler and runtime engine used by
PHP4. Developed by Zeev Suraski and Andi Gutmans, the Zend Engine is an
abbreviation of their names. In the early days of PHP4, it worked as
follows:
The PHP script was loaded by the Zend Engine and compiled into Zend
opcode. Opcodes, short for operation codes, are low level binary
instructions. Then the opcode was executed and the HTML generated sent
to the client. The opcode was flushed from memory after execution.Today, there are a multitude of products and techniques to help you
speed up this process. In the following diagram, we show the how modern
PHP scripts work; all the shaded boxes are optional.
PHP Scripts are loaded into memory and compiled into Zend opcodes.

Q:18 What are the current versions of apache, PHP, and MySQL?
A:18 As of February, 2007 the current versions arePHP: php5.2.1
MySQL: MySQL 5.2
Apache: Apache 2.2.4Note: visit http://www.php.net,

http://dev.mysql.com/downloads/mysql/,
http://www.apache.org to get current
versions.

Q:19 What are the reasons for selecting lamp (Linux, apache, MySQL,
PHP) instead of combination of other software programs, servers and
operating systems?
A:19 All of those are open source resource. Security of Linux is very
very more than windows. Apache is a better server that IIS both in
functionality and security. MySQL is world most popular open source
database. PHP is more faster that asp or any other scripting language.

Q:20 How can we encrypt and decrypt a data present in a MySQL table
using MySQL?
A:20 AES_ENCRYPT () and AES_DECRYPT ()

Q:21 How can we encrypt the username and password using PHP?
A:21 The functions in this section perform encryption and decryption, and
compression and uncompression:

encryption decryption
AES_ENCRYT() AES_DECRYPT()
ENCODE() DECODE()
DES_ENCRYPT() DES_DECRYPT()
ENCRYPT() Not available
MD5() Not available
OLD_PASSWORD() Not available
PASSWORD() Not available
SHA() or SHA1() Not available
Not available UNCOMPRESSED_LENGTH()

Q:22 What are the features and advantages of object-oriented
programming?
A:22 One of the main advantages of OO programming is its ease of
modification; objects can easily be modified and added to a system there
by reducing maintenance costs. OO programming is also considered to be
better at modeling the real world than is procedural programming. It
allows for more complicated and flexible interactions. OO systems are
also easier for non-technical personnel to understand and easier for
them to participate in the maintenance and enhancement of a system
because it appeals to natural human cognition patterns.
For some systems, an OO approach can speed development time since many
objects are standard across systems and can be reused. Components that
manage dates, shipping, shopping carts, etc. can be purchased and easily
modified for a specific system

Q:23 What are the differences between procedure-oriented languages and
object-oriented languages?
A:23 Traditional programming has the following characteristics:Functions are written sequentially, so that a change in programming can
affect any code that follows it.
If a function is used multiple times in a system (i.e., a piece of code
that manages the date), it is often simply cut and pasted into each
program (i.e., a change log, order function, fulfillment system, etc).
If a date change is needed (i.e., Y2K when the code needed to be changed
to handle four numerical digits instead of two), all these pieces of
code must be found, modified, and tested.
Code (sequences of computer instructions) and data (information on which
the instructions operates on) are kept separate. Multiple sets of code
can access and modify one set of data. One set of code may rely on data
in multiple places. Multiple sets of code and data are required to work
together. Changes made to any of the code sets and data sets can cause
problems through out the system.Object-Oriented programming takes a radically different approach:Code and data are merged into one indivisible item – an object (the
term “component” has also been used to describe an object.) An object is
an abstraction of a set of real-world things (for example, an object may
be created around “date”) The object would contain all information and
functionality for that thing (A date
object it may contain labels like January, February, Tuesday, Wednesday.
It may contain functionality that manages leap years, determines if it
is a business day or a holiday, etc., See Fig. 1). Ideally, information
about a particular thing should reside in only one place in a system.
The information within an object is encapsulated (or hidden) from the
rest of the system.
A system is composed of multiple objects (i.e., date function, reports,
order processing, etc., See Fig 2). When one object needs information
from another object, a request is sent asking for specific information.
(for example, a report object may need to know what today’s date is and
will send a request to the date object) These requests are called
messages and each object has an interface that manages messages.
OO programming languages include features such as “class”, “instance”,
“inheritance”, and “polymorphism” that increase the power and
flexibility of an object.

Q:24 What is the use of friend function?
A:24 Sometimes a function is best shared among a number of different
classes. Such functions can be declared either as member functions of
one class or as global functions. In either case they can be set to be
friends of other classes, by using a friend specifier in the class that
is admitting them. Such functions can use all attributes of the class
which names them as a friend, as if they were themselves members of that
class.
A friend declaration is essentially a prototype for a member function,
but instead of requiring an implementation with the name of that class
attached by the double colon syntax, a global function or member
function of another class provides the match.

Q:25 What are the differences between public, private, protected,
static, transient, final and volatile?
A:25 Public: Public declared items can be accessed everywhere.
Protected: Protected limits access to inherited and parent
classes (and to the class that defines the item).
Private: Private limits visibility only to the class that defines
the item.
Static: A static variable exists only in a local function scope,
but it does not lose its value when program execution leaves this scope.
Final: Final keyword prevents child classes from overriding a
method by prefixing the definition with final. If the class itself is
being defined final then it cannot be extended.
transient: A transient variable is a variable that may not
be serialized.
volatile: a variable that might be concurrently modified by multiple
threads should be declared volatile. Variables declared to be volatile
will not be optimized by the compiler because their value can change at
any time.

Q:26 What are the different types of errors in PHP?
A:26 Three are three types of errors:1. Notices: These are trivial,
non-critical errors that PHP encounters while executing a script – for
example, accessing a variable that has not yet been defined. By default,
such errors are not displayed to the user at all – although, as you will
see, you can change this default behavior.2. Warnings: These are more serious errors – for example, attempting
to include() a file which does not exist. By default, these errors are
displayed to the user, but they do not result in script termination.3. Fatal errors: These are critical errors – for example,
instantiating an object of a non-existent class, or calling a
non-existent function. These errors cause the immediate termination of
the script, and PHP’s default behavior is to display them to the user
when they take place.

Q:27 What is the functionality of the function strstr and stristr?
A:27 strstr:

Returns part of haystack
string from the first occurrence of
needle to the end of
haystack.If needle is not found,
returns FALSE.

If needle is not a
string, it is converted to an integer and applied as the
ordinal value of a character.

This function is case-sensitive. For
case-insensitive searches, use
stristr().

Q:28 What are the differences between PHP 3 and PHP 4 and PHP 5?
A:28 Please read the release notes at
http://www.php.net.

Q:29 How can we convert asp pages to PHP pages?
A:29 there are lots of tools available for asp to PHP conversion. you can
search Google for that. the best one is available athttp://asp2php.naken.cc./

Q:30 What is the functionality of the function htmlentities?
A:30 Convert all applicable characters to HTML entities
This function is identical to htmlspecialchars() in all ways, except
with htmlentities(), all characters which have HTML character entity
equivalents are translated into these entities.

Q:31 How can we get second of the current time using date function?
A:31 $second = date(”s”);

Q:32 How can we convert the time zones using PHP?
A:32 By using date_default_timezone_get and
date_default_timezone_set function on PHP 5.1.0

// Discover what 8am in Tokyo relates to on the East Coast of the US

// Set the default timezone to Tokyo time:
date_default_timezone_set(‘Asia/Tokyo’);

// Now generate the timestamp for that particular timezone, on Jan 1st, 2000
$stamp = mktime(8, 0, 0, 1, 1, 2000);

// Now set the timezone back to US/Eastern
date_default_timezone_set(‘US/Eastern’);

// Output the date in a standard format (RFC1123), this will print:
// Fri, 31 Dec 1999 18:00:00 EST
echo ‘

‘, date(DATE_RFC1123, $stamp) ,’

‘;?>

Q:33 What is meant by urlencode and urldecode?
A:33 URLencode returns a string in which all non-alphanumeric characters
except -_. have been replaced with a percent (%)
sign followed by two hex digits and spaces encoded as plus (+)
signs. It is encoded the same way that the posted data from a WWW form
is encoded, that is the same way as in
application/x-www-form-urlencoded media type.

urldecode decodes any %##
encoding in the given string.

Q:34 What is the difference between the functions unlink and unset?
A:34 unlink() deletes the given file from the file system.
unset() makes a variable undefined.

Q:35 How can we register the variables into a session?
A:35 $_SESSION[’name’] = “Mizan”;

Q:36 How can we get the properties (size, type, width, height) of an
image using PHP image functions?
A:36 To know the Image type use exif_imagetype () function
To know the Image size use getimagesize () function
To know the image width use imagesx () function
To know the image height use imagesy() function t

Q:37 How can we get the browser properties using PHP?
A:37 By using
$_SERVER[‘HTTP_USER_AGENT’]
variable.

Q:38 What is the maximum size of a file that can be uploaded using PHP
and how can we change this?
A:38 By default the maximum size is 2MB. and we can change the following
setup at php.iniupload_max_filesize = 2M

Q:39 How can we increase the execution time of a PHP script?
A:39 by changing the following setup at php.inimax_execution_time = 30
; Maximum execution time of each script, in seconds

Q:40 How can we take a backup of a MySQL table and how can we restore
it. ?
A:40 To backup: BACKUP TABLE tbl_name[,tbl_name…] TO
‘/path/to/backup/directory’
RESTORE TABLE tbl_name[,tbl_name…] FROM ‘/path/to/backup/directory’mysqldump: Dumping Table Structure and DataUtility to dump a database or a collection of database for backup or
for transferring the data to another SQL server (not necessarily a MySQL
server). The dump will contain SQL statements to create the table and/or
populate the table.
-t, –no-create-info
Don’t write table creation information (the CREATE TABLE statement).
-d, –no-data
Don’t write any row information for the table. This is very useful if
you just want to get a dump of the structure for a table!

Q:41 How can we optimize or increase the speed of a MySQL select
query?
A:41

* first of all instead of using select * from table1, use select
column1, column2, column3.. from table1
* Look for the opportunity to introduce index in the table you are
querying.
* use limit keyword if you are looking for any specific number of
rows from the result set.

Q:42 How many ways can we get the value of current session id?
A:42 session_id() returns the session id for the current session.

Q:43 How can we destroy the session, how can we unset the variable of
a session?
A:43 session_unregister — Unregister a global variable from the current
session
session_unset — Free all session variables

Q:44 How can we destroy the cookie?
A:44 Set the cookie in past.

Q:45 How many ways we can pass the variable through the navigation
between the pages?
A:45

* GET/QueryString
* POST

Q:46 What is the difference between ereg_replace() and eregi_replace()?
A:46 eregi_replace() function is identical to ereg_replace() except that
this ignores case distinction when matching alphabetic
characters.eregi_replace() function is identical to ereg_replace()
except that this ignores case distinction when matching alphabetic
characters.

Q:47 What are the different functions in sorting an array?
A:47 Sort(), arsort(),
asort(), ksort(),
natsort(), natcasesort(),
rsort(), usort(),
array_multisort(), and
uksort().

Q:48 How can we know the count/number of elements of an array?
A:48 2 ways
a) sizeof($urarray) This function is an alias of count()
b) count($urarray)

Q:49 What is the PHP predefined variable that tells the What types of
images that PHP supports?
A:49 Though i am not sure if this is wrong or not, With the exif
extension you are able to work with image meta data.

Q:50 How can I know that a variable is a number or not using a
JavaScript?
A:50 bool is_numeric ( mixed var)
Returns TRUE if var is a number or a numeric string, FALSE otherwise.or use isNaN(mixed var)The isNaN() function is used to check if a value is not a number.

Q:51 List out some tools through which we can draw E-R diagrams for
mysql.
A:51 Case Studio
Smart Draw

Q:52 How can I retrieve values from one database server and store them
in other database server using PHP?
A:52 we can always fetch from one database and rewrite to another. here
is a nice solution of it.$db1 = mysql_connect(”host”,”user”,”pwd”)
mysql_select_db(”db1″, $db1);
$res1 = mysql_query(”query”,$db1);$db2 = mysql_connect(”host”,”user”,”pwd”)
mysql_select_db(”db2″, $db2);
$res2 = mysql_query(”query”,$db2);At this point you can only fetch records from you previous ResultSet,
i.e $res1 – But you cannot execute new query in $db1, even if you
supply the link as because the link was overwritten by the new db.so at this point the following script will fail
$res3 = mysql_query(”query”,$db1); //this will failSo how to solve that?

take a look below.
$db1 = mysql_connect(”host”,”user”,”pwd”)
mysql_select_db(”db1″, $db1);
$res1 = mysql_query(”query”,$db1);

$db2 = mysql_connect(”host”,”user”,”pwd”, true)
mysql_select_db(”db2″, $db2);
$res2 = mysql_query(”query”,$db2);

So mysql_connect has another optional boolean parameter which
indicates whether a link will be created or not. as we connect to the
$db2 with this optional parameter set to ‘true’, so both link will
remain live.

now the following query will execute successfully.
$res3 = mysql_query(”query”,$db1);

Thanks goes to Hasan and Hasin for this solution.

Q:53 List out the predefined classes in PHP?
A:53 Directory
stdClass
__PHP_Incomplete_Class
exception
php_user_filter

Q:54 How can I make a script that can be bi-language (supports
English, German)?
A:54 You can maintain two separate language file for each of the
language. all the labels are putted in both language files as variables
and assign those variables in the PHP source. on runtime choose the
required language option.

Q:55 What are the difference between abstract class and interface?
A:55 Abstract class: abstract classes are the class where one or more
methods are abstract but not necessarily all method has to be abstract.
Abstract methods are the methods, which are declare in its class but not
define. The definition of those methods must be in its extending class.Interface: Interfaces are one type of class where all the methods are
abstract. That means all the methods only declared but not defined. All
the methods must be define by its implemented class.

Q:56 How can we send mail using JavaScript?
A:56 JavaScript does not have any networking capabilities as it is
designed to work on client site. As a result we can not send mails using
JavaScript. But we can call the client side mail protocol mailto
via JavaScript to prompt for an email to send. this requires the client
to approve it.

Q:57 How can we repair a MySQL table?
A:57 The syntex for repairing a MySQL table is
REPAIR TABLENAME, [TABLENAME, ], [Quick],[Extended]
This command will repair the table specified if the quick is given the
MySQL will do a repair of only the index tree if the extended is given
it will create index row by row

Q:58 What are the advantages of stored procedures, triggers, indexes?
A:58 A stored procedure is a set of SQL commands that can be compiled and
stored in the server. Once this has been done, clients don’t need to
keep re-issuing the entire query but can refer to the stored procedure.
This provides better overall performance because the query has to be
parsed only once, and less information needs to be sent between the
server and the client. You can also raise the conceptual level by having
libraries of functions in the server. However, stored procedures of
course do increase the load on the database server system, as more of
the work is done on the server side and less on the client (application)
side.Triggers will also be implemented. A trigger is effectively a type of
stored procedure, one that is invoked when a particular event occurs.
For example, you can install a stored procedure that is triggered each
time a record is deleted from a transaction table and that stored
procedure automatically deletes the corresponding customer from a
customer table when all his transactions are deleted.Indexes are used to find rows with specific column values quickly.
Without an index, MySQL must begin with the first row and then read
through the entire table to find the relevant rows. The larger the
table, the more this costs. If the table has an index for the columns in
question, MySQL can quickly determine the position to seek to in the
middle of the data file without having to look at all the data. If a
table has 1,000 rows, this is at least 100 times faster than reading
sequentially. If you need to access most of the rows, it is faster to
read sequentially, because this minimizes disk seeks.

Q:59 What is the maximum length of a table name, database name, and
fieldname in MySQL?
A:59 The following table describes the maximum length for each type of
identifier.

Identifier Maximum Length
(bytes)
Database 64
Table 64
Column 64
Index 64
Alias 255

There are some restrictions on the characters that may appear in
identifiers:

Q:60 How many values can the SET function of MySQL take?
A:60 MySQL set can take zero or more values but at the maximum it can
take 64 values

Q:61 What are the other commands to know the structure of table using
MySQL commands except explain command?
A:61 describe Table-Name;

Q:62 How many tables will create when we create table, what are they?
A:62 The ‘.frm’ file stores the table definition.
The data file has a ‘.MYD’ (MYData) extension.
The index file has a ‘.MYI’ (MYIndex) extension,

Q:63 What is the purpose of the following files having extensions 1) .frm
2) .myd 3) .myi? What do these files contain?
A:63 In MySql, the default table type is MyISAM.
Each MyISAM table is stored on disk in three files. The files have names
that begin with the table name and have an extension to indicate the
file type.
The ‘.frm’ file stores the table definition.
The data file has a ‘.MYD’ (MYData) extension.
The index file has a ‘.MYI’ (MYIndex) extension,

Q:64 What is maximum size of a database in MySQL?
A:64 If the operating system or filesystem places a limit on the number
of files in a directory, MySQL is bound by that constraint.The efficiency of the operating system in handling large numbers of
files in a directory can place a practical limit on the number of tables
in a database. If the time required to open a file in the directory
increases significantly as the number of files increases, database
performance can be adversely affected.
The amount of available disk space limits the number of tables.
MySQL 3.22 had a 4GB (4 gigabyte) limit on table size. With the MyISAM
storage engine in MySQL 3.23, the maximum table size was increased to
65536 terabytes (2567 – 1 bytes). With this larger allowed table size,
the maximum effective table size for MySQL databases is usually
determined by operating system constraints on file sizes, not by MySQL
internal limits.The InnoDB storage engine maintains InnoDB tables within a tablespace
that can be created from several files. This allows a table to exceed
the maximum individual file size. The tablespace can include raw disk
partitions, which allows extremely large tables. The maximum tablespace
size is 64TB.
The following table lists some examples of operating system file-size
limits. This is only a rough guide and is not intended to be definitive.
For the most up-to-date information, be sure to check the documentation
specific to your operating system.
Operating System File-size LimitLinux 2.2-Intel 32-bit 2GB (LFS: 4GB)
Linux 2.4+ (using ext3 filesystem) 4TB
Solaris 9/10 16TB
NetWare w/NSS filesystem 8TB
Win32 w/ FAT/FAT32 2GB/4GB
Win32 w/ NTFS 2TB (possibly larger)
MacOS X w/ HFS+ 2TB

Q:65 Give the syntax of Grant and Revoke commands?
A:65 The generic syntax for grant is as following
> GRANT [rights] on [database/s] TO [username@hostname] IDENTIFIED BY
[password]
now rights can be
a) All privileges
b) combination of create, drop, select, insert, update and delete etc.We can grant rights on all databse by using *.* or some specific
database by database.* or a specific table by database.table_name
username@hotsname can be either username@localhost, username@hostname
and username@%
where hostname is any valid hostname and % represents any name, the *.*
any condition
password is simply the password of userThe generic syntax for revoke is as following
> REVOKE [rights] on [database/s] FROM [username@hostname]
now rights can be as explained above
a) All privileges
b) combination of create, drop, select, insert, update and delete etc.
username@hotsname can be either username@localhost, username@hostname
and username@%
where hostname is any valid hostname and % represents any name, the *.*
any condition

Q:66 Explain Normalization concept?
A:66 The normalization process involves getting our data to conform to
three progressive normal forms, and a higher level of normalization
cannot be achieved until the previous levels have been achieved (there
are actually five normal forms, but the last two are mainly academic and
will not be discussed).First Normal FormThe First Normal Form (or 1NF) involves removal of redundant data
from horizontal rows. We want to ensure that there is no duplication of
data in a given row, and that every column stores the least amount of
information possible (making the field atomic).Second Normal FormWhere the First Normal Form deals with redundancy of data across a
horizontal row, Second Normal Form (or 2NF) deals with redundancy of
data in vertical columns. As stated earlier, the normal forms are
progressive, so to achieve Second Normal Form, your tables must already
be in First Normal Form.Third Normal Form

I have a confession to make; I do not often use Third Normal Form. In
Third Normal Form we are looking for data in our tables that is not
fully dependant on the primary key, but dependant on another value in
the table

Q:67 How can we find the number of rows in a table using MySQL?
A:67 Use this for mysql
>SELECT COUNT(*) FROM table_name;

Q:68 How can we find the number of rows in a result set using PHP?
A:68 $result = mysql_query($sql, $db_link);
$num_rows = mysql_num_rows($result);
echo “$num_rows rows found”;

Q:69 How many ways we can we find the current date using MySQL?
A:69 SELECT CURDATE();
CURRENT_DATE() = CURDATE()
for time use
SELECT CURTIME();
CURRENT_TIME() = CURTIME()

Q:70 What are the advantages and disadvantages of Cascading Style
Sheets?
A:70 External Style SheetsAdvantagesCan control styles for multiple documents at once. Classes can be
created for use on multiple HTML element types in many documents.
Selector and grouping methods can be used to apply styles under complex
contextsDisadvantagesAn extra download is required to import style information for each
document The rendering of the document may be delayed until the external
style sheet is loaded Becomes slightly unwieldy for small quantities of
style definitionsEmbedded Style Sheets

Advantages

Classes can be created for use on multiple tag types in the document.
Selector and grouping methods can be used to apply styles under complex
contexts. No additional downloads necessary to receive style information

Disadvantages

This method can not control styles for multiple documents at once

Inline Styles

Advantages

Useful for small quantities of style definitions. Can override other
style specification methods at the local level so only exceptions need
to be listed in conjunction with other style methods

Disadvantages

Does not distance style information from content (a main goal of
SGML/HTML). Can not control styles for multiple documents at once.
Author can not create or control classes of elements to control multiple
element types within the document. Selector grouping methods can not be
used to create complex element addressing scenarios

Q:71 What type of inheritance that PHP supports?
A:71 In PHP an extended class is always dependent on a single base class,
that is, multiple inheritance is not supported. Classes are extended
using the keyword ‘extends’.

Q:72 What is the difference between Primary Key and
Unique key?
A:72 Primary Key: A column in a table whose values uniquely identify the
rows in the table. A primary key value cannot be NULL.

Unique Key: Unique Keys are used to uniquely identify each row in the
table. There can be one and only one row for each unique key value. So
NULL can be a unique key.There can be only one primary key for a table but there can be more
than one unique for a table.

Q:73 The structure of table view buyers is as follows:

Field Type Null Key Default Extra
user_pri_id int(15) PRI null auto_increment
userid varchar(10) YES null

the value of user_pri_id the last row 999 then What will happen in
the following conditions?

Condition1: Delete all the rows and insert another row then.
What is the starting value for this auto incremented field user_pri_id ,
Condition2: Delete the last row(having the field value 999) and
insert another row then. What is the value for this auto incremented
field user_pri_id
A:73 In both cases let the value for auto increment field be n then next
row will have value n+1 i.e. 1000

Q:74 What are the advantages/disadvantages of MySQL and PHP?
A:74 Both of them are open source software (so free of cost), support
cross platform. php is faster then ASP and JSP.

Q:75 What is the difference between GROUP BY and ORDER BY in Sql?
A:75 ORDER BY [col1],[col2],…,[coln]; Tels DBMS according to what columns
it should sort the result. If two rows will hawe the same value in col1
it will try to sort them according to col2 and so on.GROUP BY
[col1],[col2],…,[coln]; Tels DBMS to group results with same value of
column col1. You can use COUNT(col1), SUM(col1), AVG(col1) with it, if
you want to count all items in group, sum all values or view average

Q:76 What is the difference between char and varchar data types?
A:76 Set char to occupy n bytes and it will take n bytes even if u r
storing a value of n-m bytes
Set varchar to occupy n bytes and it will take only the required space
and will not use the n bytes
eg. name char(15) will waste 10 bytes if we store ‘mizan’, if each char
takes a byte
eg. name varchar(15) will just use 5 bytes if we store ‘mizan’, if each
char takes a byte. rest 10 bytes will be free.

Q:77 What is the functionality of md5 function in PHP?
A:77 Calculate the md5 hash of a string. The hash is a 32-character
hexadecimal number. I use it to generate keys which I use to identify
users etc. If I add random no techniques to it the md5 generated now
will be totally different for the same string I am using.

Q:78 How can I load data from a text file into a table?
A:78 you can use LOAD DATA INFILE file_name; syntax to load data
from a text file. but you have to make sure thata) data is delimited
b) columns and data matched correctly

Q:79 How can we know the number of days between two given dates using
MySQL?
A:79 SELECT DATEDIFF(’2007-03-07′,’2005-01-01′);

Q:80 How can we know the number of days between two given dates using
PHP?
A:80 $date1 = date(’Y-m-d’);
$date2 = ‘2006-08-15′;
$days = (strtotime($date1) – strtotime($date2)) / (60 * 60 * 24);

 

Q:81 What is ‘float’ property in CSS?

A:81 The float property sets where an image or a text will appear in another element.

    

Q:82 What is descendant structure in CSS?

A:82 Descendant selectors are used to select elements that are descendants of another element in the document tree.For example, you may wish to target a specific <em> element on the page, but not all <em> elements. A sample document could contain the following code: <body>

<h1>Heading <em>here</em> </h1>

<p>Lorem ipsum dolor <em>sit</em> amet.</p>

</body> The document tree diagram (with the <em> element to be targeted) would be:Document tree showing descendant selectorsIf you use a type selector like the example below, you will select all <em> elements on the page:

 

em {color: blue; } However, if you use a descendant selector, you can refine the <em> elements that you select. The rule below will only select <em> elements that are descendants of <p> elements. If this rule is applied, the <em> element within the <h1> will not be colored blue.

 

p em {color: blue; } You can also jump levels in the document tree structure to select descendants. For example, the following code:

 

<body>

<p>Lorem ipsum dolor <em>sit</em> amet.</p>

<ul>

<li>item 1</li>

<li>item 2</li>

<li><em>item 3</em></li>

</ul>

</body> The document tree (with a third-level <em> element highlighted) would be:

 

Document tree showing descendant selectors

 

Using the following rule you can isolate any <em> element inside a <ul> element, without having to describe the <li> element. If this rule is applied, any <em> element within a <ul> element will be colored blue. However, the <em> element within the <p> will not be colored blue:

 

ul em {color: blue; } Descendant selectors are well supported across standards-compliant browsers.

    

Q:83 What is Child Descendant structure in CSS?

A:83

Child selectors

 

A child selector is used to select an element that is a direct child of another element (parent). Child selectors will not select all descendants, only direct children.

 

For example, you may wish to target an <em> that is a direct child of a <div>, but not other <em> elements that are descendants of the <div>. A sample document could contain the following code:

 

<body>

<h1>Heading <em>text</em></h1>

<div>

This is some <em>text</em>

<p>This is a paragraph of <em>text</em></p>

</div>

</body>

The document tree (highlighting the <em> that is a child of the <div>) would be:

 

Document tree showing child selector

 

Using the following rule you can target any <em> element that is a child of the <div>. Other <em> elements that are descendants but not direct children of the <div> will not be targeted.

 

div > em { color: blue; }

 

OR

 

div>em { color: blue; }

Child selectors are not supported by Windows Internet Explorer 5, 5.5 and 6, but are supported by most other standards-compliant browsers.

    

Q:84 How to create a class in JavaScript?

A:84 Classes can seem off-putting at first, but once you see the point of them, their use can be invaluable.We have already met objects. A computer object is a representation of a real object. For an estate agent the object may be a house, including information about the number of rooms and the price.An estate agent may have a lot of houses available. These houses all have different characteristics, and as objects they all go through the same processes. They are viewed, surveyed and bought, and so on.A full estate agent program would be difficult to demonstrate here, but we can introduce the use of classes.In this example, we have the house class. The house class produces house objects, all with object properties, such as number of rooms and price, and all having access to the same methods, such as sold and bought.

 

So a class can create objects with a group of properties and methods.

 

JavaScript doesn’t have a keyword specific to class, so we must go back to basics and develop classes in a different way. This isn’t very difficult.

Class Properties

 

Let us examine a very small estate agent program.

 

<HTML>

<HEAD>

<TITLE>Estate Agent</TITLE>

<SCRIPT>

function House(rooms,price,garage) {

this.rooms=rooms;

this.price=price;

this.garage=garage;

}

house1=new House(4,100000,false);

house2=new House(5,200000,true);

with (house1) document.write(’House 1 has ‘+rooms+’ rooms, ‘+(garage?’a’:’no’)+’ garage, and costs £’+price+’<BR>’);

with (house2) document.write(’House 2 has ‘+rooms+’ rooms, ‘+(garage?’a’:’no’)+’ garage, and costs £’+price+’<BR>’);

</SCRIPT>

</HEAD>

</HTML>

 

We define a House function that takes three parameters, rooms, price and garage. The function uses the this keyword to create an object.

 

When we call the House function, we assign the result to our variable, which becomes an object.

 

So, identical code would be:

 

house1=new Object();

house1.rooms=4;

house1.price=100000;

house1.garage=false;

 

We would have to type this in for all houses, which would be very tedious and is why we use the class structure instead.

 

When we display the details for a house, I have introduced the ternary operator, ‘?:’. The ternary operator is a compacted version of:

 

if (garage) str=’a’; else str=’no’;

 

(garage?’a’:’no’) means if garage is true, return ‘a’ else return ‘no’. Using the ternary operator removes a line of code, and avoids having to create a new variable.

Class Methods

 

The House class we have so far defined only contains object properties. We could add a method to replace the document.write() action we used before. (See example)

 

<HTML>

<HEAD>

<TITLE>Estate Agent 2</TITLE>

<SCRIPT>

function House(name,rooms,price,garage) {

this.name=name;

this.rooms=rooms;

this.price=price;

this.garage=garage;

this.view=view;

}

function view() {

with (this) document.write(name+’ has ‘+rooms+’ rooms, ‘+(garage?’a’:’no’)+’ garage, and costs £’+price+’<BR>’);

}

house1=new House(’House 1′,4,100000,false);

house2=new House(’Big House’,5,200000,true);

house1.view();

house2.view();

</SCRIPT>

</HEAD>

</HTML>

 

Much better!

 

Note how we must add another property, name, so that we can identify the house in question. This offers more flexibility than re-using the variable name, and the variable name is inaccessible anyway, i.e. it is very difficult, if not impossible, to get the view() function to use the string ‘house1′.

    

Q:85 Are namespaces are there in JavaScript?

A:81 A namespace is a container and allows you to bundle up all your functionality using a unique name. In JavaScript, a namespace is really just an object that you’ve attached all further methods, properties and objects. But it is not always necessary to use namespace.

    

Q:86 What is JSON? What are the notations used in JSON?

A:86 JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. It is based on a subset of the JavaScript Programming Language, Standard ECMA-262 3rd Edition – December 1999. JSON is a text format that is completely language independent but uses conventions that are familiar to programmers of the C-family of languages, including C, C++, C#, Java, JavaScript, Perl, Python, and many others. These properties make JSON an ideal data-interchange language.

    

Q:87 How to get Query String in PHP for http request?

A:87 $_GET[] and $_REQUEST[]

    

Q:88 How to get the http Request in PHP?

A:88 When PHP is used on a Web server to handle a HTTP request, it converts information submitted in the HTTP request as predefined variables:

 

    * $_GET – Associate array of variables submitted with GET method.

    * $_POST – Associate array of variables submitted with POST method.

    * $_COOKIE – Associate array of variables submitted as cookies.

    * $_REQUEST – Associate array of variables from $_GET, $_POST, and $_COOKIE.

    * $_SERVER – Associate array of all information from the server and the HTTP request.

 

    

Q:89 How you provide security for PHP application?

A:89 There are many ways to accomplish the security tasks but the most common 7 ways are1. Validate Input. Never trust your user and always filter input before taking it to any operation.2. Provide access control.3. Session ID protection4. preventing Cross Site Scripting (XSS) flaws

 

5. SQL injection vulnerabilities.

 

6. Turning off error reporting and exposing to the site for hackers. Instead use log file to catch exceptions

 

7. Effective Data handling

    

Q:90 What is SQL Injection in PHP security?

A:90 SQL injection attacks are extremely simple to defend against, but many applications are still vulnerable. Consider the following SQL statement:

 

<?php

$sql = “INSERT

        INTO   users (reg_username,

                      reg_password,

                      reg_email)

        VALUES (‘{$_POST[‘reg_username’]}’,

                ‘$reg_password’,

                ‘{$_POST[‘reg_email’]}’)”;

?>

 

This query is constructed with $_POST, which should immediately look suspicious.

 

Assume that this query is creating a new account. The user provides a desired username and an email address. The registration application generates a temporary password and emails it to the user to verify the email address. Imagine that the user enters the following as a username:

 

bad_guy’, ‘mypass’, ”), (‘good_guy

 

This certainly doesn’t look like a valid username, but with no data filtering in place, the application can’t tell. If a valid email address is given (shiflett@php.net, for example), and 1234 is what the application generates for the password, the SQL statement becomes the following:

 

<?php

 

$sql = “INSERT

        INTO   users (reg_username,

                      reg_password,

                      reg_email)

        VALUES (‘bad_guy’, ‘mypass’, ”),

          (‘good_guy’,

                ‘1234’,

                ‘shiflett@php.net’)”; ?>

 

Rather than the intended action of creating a single account (good_guy) with a valid email address, the application has been tricked into creating two accounts, and the user supplied every detail of the bad_guy account.

 

While this particular example might not seem so harmful, it should be clear that worse things could happen once an attacker can make modifications to your SQL statements.

 

For example, depending on the database you are using, it might be possible to send multiple queries to the database server in a single call. Thus, a user can potentially terminate the existing query with a semicolon and follow this with a query of the user’s choosing.

 

MySQL, until recently, does not allow multiple queries, so this particular risk is mitigated. Newer versions of MySQL allow multiple queries, but the corresponding PHP extension (ext/mysqli) requires that you use a separate function if you want to send multiple queries (mysqli_multi_query() instead of mysqli_query()). Only allowing a single query is safer, because it limits what an attacker can potentially do.

 

Protecting against SQL injection is easy:

 

    * Filter your data.This cannot be overstressed. With good data filtering in place, most security concerns are mitigated, and some are practically eliminated.

    * Quote your data.If your database allows it (MySQL does), put single quotes around all values in your SQL statements, regardless of the data type.

    * Escape your data.Sometimes valid data can unintentionally interfere with the format of the SQL statement itself. Use mysql_escape_string() or an escaping function native to your particular database. If there isn’t a specific one, addslashes() is a good last resort.

 

    

Q:91 What is cross site Scripting?

A:91 To understand what Cross Site Scripting is, let’s see a usual situation, common to many sites. Let’s say we are taking some information passed in on a querystring (the string after the (?) character within a URL), with the purpose of displaying the content of a variable, for example, the visitor’s name:

 

http://www.yourdomain.com/welcomedir/welcomepage.php?name=John

As we can see in this simple querystring, we are passing the visitor’s name as a parameter in the URL, and then displaying it on our “welcomepage.php” page with the following PHP code:

 

<?php

 

echo ‘Welcome to our site ’ . stripslashes($_GET[‘name’]);

 

?>

The result of this snippet is shown below:

 

Welcome to our site John

This is pretty simple and straightforward. We’re displaying the content of the “name” variable, by using the $_GET superglobal PHP array, as we have done probably hundreds of times. Everything seems to be fine. Now, what’s wrong with this code? Nothing really. But let’s modify the querystring by replacing our visitor’s name passed in the URL:

 

http://www.yourdomain.com/welcomedir/

welcomepage.php?name=John

with something like this:

 

http://www.yourdomain.com/welcomedir/

welcomepage.php?name=

<script language=javascript>alert

(‘Hey, you are going to be hijacked!’);</script>

Do you remember the PHP code included in our “welcome.php” page? Yes, you’re correct. When we modify the querystring, the following code is executed:

 

<?php

 

echo ‘Welcome to our site ‘ .

<script language=javascript> alert(‘Hey, you are going

to be hijacked!’);</script>

 

?>

The output of this code is an alert JavaScript box telling you “Hey, you are going be hijacked!” after the “Welcome to our site” phrase.

 

Very ugly stuff, right? That’s a simple example of the Cross Site Scripting vulnerability. This means that any pasted JavaScript code into the URL will be executed happily with no complaints at all.

 

    

Q:92 Which method do you follow to get a record from a million records? (Searching, …. not from database, from an array in php)

A:92 use array_search(), array_keys(), array_values(), array_key_exists(), and in_array().

    

Q:93 Which sorting method is lowest time consumable?

A:93 HeapSort, Merge sort are the lowest time consumable sorting algorithm.

    

Q:94 Which sorting method is lowest memory consumable?

A:94

Difference between php4 & php5

Differences between PHP4 and PHP5

Here’s a quick overview of what has changed between PH4 and PHP5. PHP5 for the most part is backwards compatible with PHP4, but there are a couple key changes that might break your PHP4 script in a PHP5 environment. If you aren’t already, I stronly suggest you start developing for PHP5. Many hosts these days offer a PHP5 environment, or a dual PHP4/PHP5 setup so you should be fine on that end. Using all of these new features is worth even a moderate amount of trouble you might go through finding a new host!

Note: Some of the features listed below are only in PHP5.2 and above.

Object Model
The new OOP features in PHP5 is probably the one thing that everyone knows for sure about. Out of all the new features, these are the ones that are talked about most!

Passed by Reference
This is an important change. In PHP4, everything was passed by value, including objects. This has changed in PHP5 — all objects are now passed by reference.

 

PHP Code:

$joe = new Person();
$joe->sex = 'male';  

$betty = $joe;
$betty->sex = 'female';

echo $joe->sex; // Will be 'female'  


The above code fragment was common in PHP4. If you needed to duplicate an object, you simply copied it by assigning it to another variable. But in PHP5 you must use the new clone keyword.

 

Note that this also means you can stop using the reference operator (&). It was common practice to pass your objects around using the & operator to get around the annoying pass-by-value functionality in PHP4.

Class Constants and Static Methods/Properties
You can now create class constants that act much the same was as define()’ed constants, but are contained within a class definition and accessed with the :: operator.

Static methods and properties are also available. When you declare a class member as static, then it makes that member accessible (through the :: operator) without an instance. (Note this means within methods, the $this variable is not available)

Visibility
Class methods and properties now have visibility. PHP has 3 levels of visibility:

1. Public is the most visible, making methods accessible to everyone and properties readable and writable by everyone.
2. Protected makes members accessible to the class itself and any subclasses as well as any parent classes.
3. Private makes members only available to the class itself.

Unified Constructors and Destructors
PHP5 introduces a new unified constructor/destructor names. In PHP4, a constructor was simply a method that had the same name as the class itself. This caused some headaches since if you changed the name of the class, you would have to go through and change every occurrence of that name.

In PHP5, all constructors are named __construct(). That is, the word construct prefixed by two underscores. Other then this name change, a constructor works the same way.

Also, the newly added __destruct() (destruct prefixed by two underscores) allows you to write code that will be executed when the object is destroyed.

Abstract Classes
PHP5 lets you declare a class as abstract. An abstract class cannot itself be instantiated, it is purely used to define a model where other classes extend. You must declare a class abstract if it contains any abstract methods. Any methods marked as abstract must be defined within any classes that extend the class. Note that you can also include full method definitions within an abstract class along with any abstract methods.

Interfaces
PHP5 introduces interfaces to help you design common APIs. An interface defines the methods a class must implement. Note that all the methods defined in an interface must be public. An interface is not designed as a blueprint for classes, but just a way to standardize a common API.

The one big advantage to using interfaces is that a class can implement any number of them. You can still only extend on parent class, but you can implement an unlimited number of interfaces.

Magic Methods
There are a number of “magic methods” that add an assortment to functionality to your classes. Note that PHP reserves the naming of methods prefixed with a double-underscore. Never name any of your methods with this naming scheme!

Some magic methods to take note of are __call, __get, __set and __toString. These are the ones I find most useful.

Finality
You can now use the final keyword to indicate that a method cannot be overridden by a child. You can also declare an entire class as final which prevents it from having any children at all.

The __autoload Function
Using a specially named function, __autoload (there’s that double-underscore again!), you can automatically load object files when PHP encounters a class that hasn’t been defined yet. Instead of large chunks of include’s at the top of your scripts, you can define a simple autoload function to include them automatically.

PHP Code:

function __autoload($class_name) {
     require_once "./includes/classes/$class_name.inc.php";
}  


Note you can change the autoload function or even add multiple autoload functions using spl_autoload_register and related functions.

 

Standard PHP Library
PHP now includes a bunch of functionality to solve common problems in the so-named SPL. There’s a lot of cool stuff in there, check it out!

For example, we can finally create classes that can be accessed like arrays by implementing the ArrayAccess interface. If we implement the Iterator interface, we can even let our classes work in situations like the foreach construct.

Miscellaneous Features

Type Hinting
PHP5 introduces limited type hinting. This means you can enforce what kind of variables are passed to functions or class methods. The drawback is that (at this time), it will only work for classes or arrays — so no other scalar types like integers or strings.

To add a type hint to a parameter, you specify the name of the class before the $. Beware that when you specify a class name, the type will be satisfied with all of its subclasses as well.

PHP Code:

function echo_user(User $user) {
    echo $user->getUsername();
}  


If the passed parameter is not User (or a subclass of User), then PHP will throw a fatal error.

Exceptions
PHP finally introduces exceptions! An exception is basically an error. By using an exception however, you gain more control the simple trigger_error notices we were stuck with before.

An exception is just an object. When an error occurs, you throw an exception. When an exception is thrown, the rest of the PHP code following will not be executed. When you are about to perform something “risky”, surround your code with atry block. If an exception is thrown, then your following catch block is there to intercept the error and handle it accordingly. If there is no catch block, a fatal error occurs.

PHP Code:

try {
    $cache->write();
} catch (AccessDeniedException $e) {
    die('Could not write the cache, access denied.');
} catch (Exception $e) {
   die('An unknown error occurred: ' . $e->getMessage());
}  


E_STRICT Error Level
There is a new error level defined as E_STRICT (value 2048). It is not included in E_ALL, if you wish to use this new level you must specify it explicitly. E_STRICT will notify you when you use depreciated code. I suggest you enable this level so you can always stay on top of things.

Foreach Construct and By-Reference Value
The foreach construct now lets you define the ‘value’ as a reference instead of a copy. Though I would suggest againstusing this feature, as it can cause some problems if you aren’t careful:

PHP Code:

foreach($array as $k => &$v) {
    // Nice and easy, no working with $array[$k] anymore
    $v = htmlentities($v);
}  

// But be careful, this will have an unexpected result because
// $v will still be a reference to the last element of the $array array
foreach($another_array as $k => $v) {

}  


New Functions
PHP5 introduces a slew of new functions. You can get a list of them from the PHP Manual.

New Extensions
PHP5 also introduces new default extensions.

• SimpleXML for easy processing of XML data
• DOM and XSL extensions are available for a much improved XML-consuming experience. A breath of fresh air after using DOMXML for PHP4!
• PDO for working with databases. An excellent OO interface for interacting with your database.
• Hash gives you access to a ton of hash functions if you need more then the usual md5 or sha1.

Compatibility Issues
The PHP manual has a list of changes that will affect backwards compatibility. You should definately read through that page, but here is are three issues I have found particularly tiresome:

• array_merge() will now give you warnings if any of the parameters are not arrays. In PHP4, you could get away with merging non-arrays with arrays (and the items would just be added if they were say, a string). Of course it was bad practice to do this to being with, but it can cause headaches if you don’t know about it.
• As discussed above, objects are now passed by references. If you want to copy a object, make sure to use theclone keyword.
• get_*() now return names as they were defined. If a class was called MyTestClass, then get_class() will return that — case sensitive! In PHP4, they were always returned in lowercase.

Freshers PHP/MySQL Technical Interview Questions & Answers

Freshers PHP Technical Interview Questions & Answers

Question : What are the differences between Get and post methods in form submitting. Give the case where we can use get and we can use post methods?

Answer : When to use GET or POST

The HTML 2.0 specification says, in section Form Submission (and the HTML 4.0 specification repeats this with minor stylistic changes):

–>If the processing of a form is idempotent (i.e. it has no lasting observable effect on the state of the
world), then the form method should be GET. Many database searches have no visible side-effects and make ideal applications of query forms.
–
–>If the service associated with the processing of a form has side effects (for example, modification of a database or subscription to a service), the method should be POST.

How the form data is transmitted?

quotation from the HTML 4.0 specification

–> If the method is “get” – -, the user agent takes the value of action, appends a ? to it, then appends the form data set, encoded using the application/x-www-form-urlencoded content type. The user agent then traverses the link to this URI. In this scenario, form data are restricted to ASCII codes.
–> If the method is “post” –, the user agent conducts an HTTP post transaction using the value of the action attribute and a message created according to the content type specified by the enctype
attribute.

Quote from CGI FAQ

Firstly, the the HTTP protocol specifies differing usages for the two methods. GET requests should always be idempotent on the server. This means that whereas one GET request might (rarely) change some state on the Server, two or more identical requests will have no further effect.

This is a theoretical point which is also good advice in practice. If a user hits “reload” on his/her browser, an identical request will be sent to the server, potentially resulting in two identical database or guestbook entries, counter increments, etc. Browsers may reload a GET URL automatically, particularly if cacheing is disabled (as is usually the case with CGI output), but will typically prompt the user before re-submitting a POST request. This means you’re far less likely to get inadvertently-repeated entries from POST.

GET is (in theory) the preferred method for idempotent operations, such as querying a database, though it matters little if you’re using a form. There is a further practical constraint that many systems have built-in limits to the length of a GET request they can handle: when the total size of a request (URL+params) approaches or exceeds 1Kb, you are well-advised to use POST in any
case.

I would prefer POST when I don’t want the status to be change when user resubmits. And GET
when it does not matter.

Question : Who is the father of PHP and explain the changes in PHP versions?

Answer : Rasmus Lerdorf is known as the father of PHP.PHP/FI 2.0 is an early and no longer supported version of PHP. PHP 3 is the successor to PHP/FI 2.0 and is a lot nicer. PHP 4 is the current generation of PHP, which uses the Zend engine under the hood. PHP 5 uses Zend engine 2 which, among other things, offers many additional OOPs features.

Question : How can we submit a form without a submit button?

Answer : The main idea behind this is to use Java script submit() function in order to submit the form without explicitly clicking any submit button. You can attach the document.formname.submit() method to onclick, onchange events of different inputs and perform the form submission. you
can even built a timer function where you can automatically submit the form after xx seconds once the loading is done (can be seen in online test sites).

Question : In how many ways we can retrieve the data in the result set of
MySQL using PHP?

Answer : You can do it by 4 Ways

1. mysql_fetch_row.
2. mysql_fetch_array
3. mysql_fetch_object
4. mysql_fetch_assoc

Question : What is the difference between mysql_fetch_object and
mysql_fetch_array?

Answer : mysql_fetch_object() is similar to mysql_fetch_array(), with one difference –
an object is returned, instead of an array. Indirectly, that means that you can only access the data by the field names, and not by their offsets (numbers are illegal property names).

Question : What is the difference between $message and $$message?

Answer : It is a classic example of PHP’s variable variables. take the following example.

$message = “Raghav”;

$$message = “is a owner of https://sharag.wordpress.com/ “;

$message is a simple PHP variable that we are used to. But the $$message is not a very familiar face. It creates a variable name $mizan with the value “is a moderator of PHPXperts.” assigned. break it like this${$message} => $mizanSometimes it is convenient to be able to have variable variable names. That is, a variable name which can be set and used dynamically.

Question : How can we extract string ‘hotmail.com ‘ from a string raghav.cool@hotmail.com using regular expression of PHP?

Answer : preg_match(”/^http://.+@(.+)$/”,’raghav.cool@hotmail.com’,$found);
echo $found[1];

Question : How can we create a database using PHP and MySQL?

Answer : We can create MySQL Database with the use of mysql_create_db(“Database Name”).

Question : What are the differences between require and include, include_once and require_once?

Answer :

The include() statement includes and evaluates the specified file.The documentation below also applies to require(). The two constructs are identical in every way except how they handle
failure. include() produces a Warning while require() results in a Fatal Error. In other words, use
require() if you want a missing file to halt processing of the page. include() does not behave this way, the script will continue regardless. The include_once() statement includes and evaluates the
specified file during the execution of the script. This is a behavior similar to the include() statement, with the only difference being that if the code from a file has already been included, it will not be
included again. As the name suggests, it will be included just once.include_once() should be used in cases where the same file might be included and evaluated more than once during a particular execution of a script, and you want to be sure that it is included exactly once to avoid problems with function redefinitions, variable value reassignments, etc. require_once() should be used in cases where the same file might be included and evaluated more than once during a particular execution of a script, and you want to be sure that it is included exactly once to avoid problems with function
redefinitions, variable value reassignments, etc.

Question : Can we use include (”abc.PHP”) two times in a PHP page “makeit.PHP”?

Answer : Yes we can use include() more than one time in any page though it is not a very good practice.

Question : What are the different tables present in MySQL, which type of table is generated when we are creating a table in the following syntax:
create table employee (eno int(2),ename varchar(10)) ?

Answer : Total 5 types of tables we can create
1. MyISAM
2. Heap
3. Merge
4. INNO DB
5. ISAM
MyISAM is the default storage engine as of MySQL 3.23 and as a result if
we do not specify the table name explicitly it will be assigned to the
default engine.

Question : Functions in IMAP, POP3 AND LDAP?

Answer : You can find these specific information in PHP Manual.

Question : How can I execute a PHP script using command line?

Answer : As of version 4.3.0, PHP supports a new SAPI type (Server Application Programming Interface) named CLI which means Command Line Interface. Just run the PHP CLI (Command Line Interface) program and provide the PHP script file name as the command line argument. For example, “php myScript.php”, assuming “php” is the command to invoke the CLI program.
Be aware that if your PHP script was written for the Web CGI interface, it may not execute properly in command line environment.

Question : Suppose your Zend engine supports the mode <? ?>. Then how can you
configure your PHP Zend engine to support <?php ?>mode ?

Answer : In php.ini file:
set
short_open_tag=on
to make PHP support

Question : Shopping cart online validation i.e. how can we configure Paypal,
etc.?

Answer : We can find the detail documentation about different paypal integration process at the following site PayPal PHP
SDK : http://www.paypaldev.org/

Question : What is meant by nl2br()?

Answer : Inserts HTML line breaks
(
)
before all newlines in a string string nl2br (string); Returns string with ” inserted before all newlines.
For example: echo nl2br(”god bless/n you”) will output “god bless
you” to your browser.

Question : Draw the architecture of Zend engine?

Answer : The Zend Engine is the internal compiler and runtime engine used by PHP4. Developed by Zeev Suraski and Andi Gutmans, the Zend Engine is an
abbreviation of their names. In the early days of PHP4, it worked as follows:

The PHP script was loaded by the Zend Engine and compiled into Zend opcode. Opcodes, short for operation codes, are low level binary instructions. Then the opcode was executed and the HTML generated sent to the client. The opcode was flushed from memory after execution.Today, there are a multitude of products and techniques to help you speed up this process. In the following diagram, we show the how modern PHP scripts work; all the shaded boxes are optional.

PHP Scripts are loaded into memory and compiled into Zend opcodes.

Question : What are the current versions of apache, PHP, and MySQL?

Answer : As of Aug 2008 the current versions are PHP: php5.2.6
MySQL: MySQL 5.1.2
Apache: Apache 2.2.9
Note: visit
http://www.php.net/,
http://dev.mysql.com/downloads/mysql/,
http://www.apache.org/ to get current
versions.

Question : What are the reasons for selecting lamp (Linux, apache, MySQL,
PHP) instead of combination of other software programs, servers and operating systems?

Answer : All of those are open source resource. Security of Linux is very very more than windows. Apache is a better server that IIS both in functionality and security. MySQL is world most popular open source database. PHP is more faster that asp or any other scripting language.

Question : How can we encrypt and decrypt a data present in a MySQL table using MySQL?

Answer : AES_ENCRYPT () and AES_DECRYPT ()

Question : How can we encrypt the username and password using PHP?

Answer : The functions in this section perform encryption and decryption, and
compression and uncompression:

Encryption	Decryption
AES_ENCRYT()	AES_DECRYPT()
ENCODE()	DECODE()
DES_ENCRYPT()	DES_DECRYPT()
ENCRYPT()	Not available
MD5()	Not available
OLD_PASSWORD()	Not available
PASSWORD()	Not available
SHA() or SHA1()	Not available
Not available	UNCOMPRESSED_LENGTH()

Question : What are the features and advantages of object-oriented programming?

Answer : One of the main advantages of OO programming is its ease of modification; objects can easily be modified and added to a system there by reducing maintenance costs. OO programming is also considered to be better at modeling the real world than is procedural programming. It allows for more complicated and flexible interactions. OO systems are also easier for non-technical personnel to understand and easier for them to participate in the maintenance and enhancement of a system because it appeals to natural human cognition patterns. For some systems, an OO approach can speed development time since many objects are standard across systems and can be reused. Components that manage dates, shipping, shopping carts, etc. can be purchased and easily modified for a specific system.

Question : What are the differences between procedure-oriented languages and
object-oriented languages?

Answer : Traditional programming has the following characteristics:Functions are written sequentially, so that a change in programming can affect any code that follows it. If a function is used multiple times in a system (i.e., a piece of code that manages the date), it is often simply cut and pasted into each program (i.e., a change log, order function, fulfillment system, etc). If a date change is needed (i.e., Y2K when the code needed to be changed to handle four numerical digits instead of two), all these pieces of code must be found, modified, and tested. Code (sequences of computer instructions) and data (information on which the instructions operates on) are kept separate. Multiple sets of code can access and modify one set of data. One set of code may rely on data in multiple places. Multiple sets of code and data are required to work together. Changes made to any of the code sets and data sets can cause problems through out the system.Object-Oriented programming takes a radically different approach:Code and data are merged into one indivisible item – an object (the term “component” has also been used to describe an object.) An object is an abstraction of a set of real-world things (for example, an object may be created around “date”) The object would contain all information and
functionality for that thing (A date object it may contain labels like January, February, Tuesday, Wednesday.
It may contain functionality that manages leap years, determines if it is a business day or a holiday, etc., See Fig. 1). Ideally, information about a particular thing should reside in only one place in a system.The information within an object is encapsulated (or hidden) from the rest of the system. A system is composed of multiple objects (i.e., date function, reports, order processing, etc., See Fig 2). When one object needs information from another object, a request is sent asking for specific information. (for example, a report object may need to know what today’s date is and will send a request to the date object) These requests are called messages and each object has an interface that manages messages. OO programming languages include features such as “class”, “instance”, “inheritance”, and “polymorphism” that increase the power and
flexibility of an object.

Question : What is the use of friend function?

Answer : Sometimes a function is best shared among a number of different classes. Such functions can be declared either as member functions of one class or as global functions. In either case they can be set to be friends of other classes, by using a friend specifier in the class that is admitting them. Such functions can use all attributes of the class which names them as a friend, as if they were themselves members of that class. A friend declaration is essentially a prototype for a member function, but instead of requiring an implementation with the name of that class attached by the double colon syntax, a global function or member function of another class provides the match.

Question : What are the differences between public, private, protected,static, transient, final and volatile?

Answer : Public: Public declared items can be accessed everywhere.
Protected: Protected limits access to inherited and parent classes (and to the class that defines the item).
Private: Private limits visibility only to the class that defines the item.
Static: A static variable exists only in a local function scope, but it does not lose its value when program execution leaves this scope.
Final: Final keyword prevents child classes from overriding a method by prefixing the definition with final. If the class itself is being defined final then it cannot be extended.
Transient: A transient variable is a variable that may not be serialized.
Volatile: a variable that might be concurrently modified by multiple threads should be declared volatile. Variables declared to be volatile will not be optimized by the compiler because their value can change at any time.

Question : What are the different types of errors in PHP?

Answer : Three are three types of errors:1. Notices: These are trivial, non-critical errors that PHP encounters while executing a script – for example, accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all – although, as you will see, you can change this default behavior.2. Warnings: These are more serious errors – for example, attempting to include() a file which does not exist. By default, these errors are displayed to the user, but they do not result in script termination.3. Fatal errors: These are critical errors – for example,
instantiating an object of a non-existent class, or calling a non-existent function. These errors cause the immediate termination of the script, and PHP’s default behavior is to display them to the user when they take place.

Question : What is the functionality of the function strstr and stristr?

Answer : strstr:
Returns part of haystack string from the first occurrence of needle to the end of haystack.If needle is not found, returns FALSE. If needle is not a string, it is converted to an integer and applied as the ordinal value of a character. This function is case-sensitive. For case-insensitive searches, use stristr().

Question : What are the differences between PHP 3 and PHP 4 and PHP 5?

Answer : PHP 3 is most procedure oriented and , PHP4 and PHP5 aer object oriented. For more details
http://php.net/

Question : How can we convert asp pages to PHP pages?

Answer : There are lots of tools available for asp to PHP conversion. you can search Google for that. the best one is available at http://asp2php.naken.cc/

Question : What is the functionality of the function htmlentities?

Answer : Convert all applicable characters to HTML entities
This function is identical to htmlspecialchars() in all ways, except with htmlentities(), all characters which have HTML character entity equivalents are translated into these entities.

Question : How can we get second of the current time using date function?

Answer : $second = date(”s”);

Question : How can we convert the time zones using PHP?

Answer : By using date_default_timezone_get and
date_default_timezone_set function on PHP 5.1.0
<!–p// Discover what 8am in Tokyo relates to on the East Coast of the US

// Set the default timezone to Tokyo time:
date_default_timezone_set(’Asia/Tokyo’);

// Now generate the timestamp for that particular timezone, on Jan 1st, 2000
$stamp = mktime(8, 0, 0, 1, 1, 2000);

// Now set the timezone back to US/Eastern
date_default_timezone_set(’US/Eastern’);

// Output the date in a standard format (RFC1123), this will  print:
// Fri, 31 Dec 1999 18:00:00 EST
echo ‘

‘, date(DATE_RFC1123, $stamp) ,’

‘; ?>

Question : What is meant by urlencode and urldecode?

Answer : URLencode returns a string in which all non-alphanumeric characters except -_. have been replaced with a percent (%) sign followed by two hex digits and spaces encoded as plus (+) signs. It is encoded the same way that the posted data from a WWW form
is encoded, that is the same way as in application/x-www-form-urlencoded media type. urldecode decodes any %## encoding in the given string.

Question : What is the difference between the functions unlink and unset?

Answer : unlink() deletes the given file from the file system.
unset() makes a variable undefined.

Question : How can we register the variables into a session?

Answer : $_SESSION[’name’] = “RAGHAV”;

Question : How can we get the properties (size, type, width, height) of an image using PHP image functions?

Answer : To know the Image type use exif_imagetype () function
To know the Image size use getimagesize () function
To know the image width use imagesx () function
To know the image height use imagesy() function

Question : How can we get the browser properties using PHP?

Answer : By using
$_SERVER[’HTTP_USER_AGENT’] variable.

Question : What is the maximum size of a file that can be uploaded using PHP
and how can we change this?

Answer : By default the maximum size is 2MB. and we can change the following setup at php.iniupload_max_filesize = 2M

Question : How can we increase the execution time of a PHP script?

Answer : by changing the following setup at php.inimax_execution_time = 30; Maximum execution time of each script, in seconds

Question : How can we take a backup of a MySQL table and how can we restore it. ?

Answer : To backup: BACKUP TABLE tbl_name[,tbl_name…] TO ‘/path/to/backup/directory’
RESTORE TABLE tbl_name[,tbl_name…] FROM ‘/path/to/backup/directory’mysqldump: Dumping Table Structure and DataUtility to dump a database or a collection of database for backup or for transferring the data to another SQL server (not necessarily a MySQL server). The dump will contain SQL statements to create the table and/or populate the table. -t, –no-create-info Don’t write table creation information (the CREATE TABLE statement). -d, –no-data Don’t write any row information for the table. This is very useful if you just want to get a dump of the structure for a table!

Question : How can we optimize or increase the speed of a MySQL select query?

Answer : • First of all instead of using select * from table1, use select column1, column2, column3.. from table1
•Look for the opportunity to introduce index in the table you are  querying.
•use limit keyword if you are looking for any specific number of rows from the result set.

Question : How many ways can we get the value of current session id?

Answer : session_id() returns the session id for the current session.

Question : How can we destroy the session, how can we unset the variable of a session?

Answer : session_unregister — Unregister a global variable from the current session

session_unset — Free all session variables

Question : How can we destroy the cookie?

Answer : Set the cookie in past.

Question : How many ways we can pass the variable through the navigation between the pages?

Answer : •GET/QueryString
•POST

Question : What is the difference between ereg_replace() and eregi_replace()?

Answer : eregi_replace() function is identical to ereg_replace() except that this ignores case distinction when matching alphabetic characters.eregi_replace() function is identical to ereg_replace() except that this ignores case distinction when matching alphabetic characters.

Question : What are the different functions in sorting an array?

Answer : Sort(), arsort(),
asort(), ksort(),
natsort(), natcasesort(),
rsort(), usort(),
array_multisort(), and
uksort().

Question : How can we know the count/number of elements of an array?

Answer : 2 ways
a) sizeof($urarray) This function is an alias of count()
b) count($urarray)

Question : What is the PHP predefined variable that tells the What types of
images that PHP supports?

Answer : Though i am not sure if this is wrong or not, With the exif extension you are able to work with image meta data.

Question : How can I know that a variable is a number or not using a JavaScript?

Answer : bool is_numeric ( mixed var) Returns TRUE if var is a number or a numeric string, FALSE otherwise.or use isNaN(mixed var)The isNaN() function is used to check if a value is not a number.

Question : List out some tools through which we can draw E-R diagrams for mysql.

Answer :
Case Studio
Smart Draw

Question : How can I retrieve values from one database server and store themin other database server using PHP?

Answer : WeWe can always fetch from one database and rewrite to another. Here is a nice solution of it.
$db1 = mysql_connect(”host”,”user”,”pwd”);
mysql_select_db(”db1?, $db1);
$res1 = mysql_query(”query”,$db1);
$db2 = mysql_connect(”host”,”user”,”pwd”);
mysql_select_db(”db2?, $db2);
$res2 = mysql_query(”query”,$db2);
At this point you can only fetch records from you previous ResultSet, i.e $res1 – But you cannot execute new query in $db1, even if yousupply the link as because the link was overwritten by the new db.so at this point the following script will fail
$res3 = mysql_query(”query”,$db1); //this will failSo how to solve that? take a look below.
$db1 = mysql_connect(”host”,”user”,”pwd”);
mysql_select_db(”db1?, $db1);
$res1 = mysql_query(”query”,$db1);
$db2 = mysql_connect(”host”,”user”,”pwd”, true);
mysql_select_db(”db2?, $db2);
$res2 = mysql_query(”query”,$db2);
So mysql_connect has another optional boolean parameter whichindicates whether a link will be created or not. As we connect to the $db2 with this optional parameter set to ‘true’, so both link willremain live. Now the following query will execute successfully.
$res3 = mysql_query(”query”,$db1);

Question : List out the predefined classes in PHP?

Answer : Directory
stdClass
__PHP_Incomplete_Class
exception
php_user_filter

Question : How can I make a script that can be bi-language (supports  English, German)?

Answer : You can maintain two separate language file for each of the language. All the labels are putted in both language files as variables and assign those variables in the PHP source. On run-time choose the required language option.

Question : What are the difference between abstract class and interface?

Answer : Abstract class: abstract classes are the class where one or moremethods are abstract but not necessarily all method has to be abstract.

Abstract methods are the methods, which are declare in its class but not defined. The definition of those methods must be in its extending class.

Interface: Interfaces are one type of class where all the methods are abstract. That means all the methods only declared but not defined. All the methods must be defined by its implemented class.

Question : How can we send mail using JavaScript?

Answer : JavaScript does not have any networking capabilities as it isdesigned to work on client site. As a result we can not send mails usingJavaScript. But we can call the client side mail protocol mailtovia JavaScript to prompt for an Email  to send. this requires the client to approve it.

Question : How can we repair a MySQL table?

Answer : The syntex for repairing a MySQL table is REPAIR TABLENAME, [TABLENAME, ], [Quick],[Extended].This command will repair the table specified if the quick is given the MySQL will do a repair of only the index tree if the extended is givenit will create index row by row.

Question : What are the advantages of stored procedures, triggers, indexes?

Answer : A stored procedure is a set of SQL commands that can be compiled andstored in the server. Once this has been done, clients don’t need tokeep re-issuing the entire query but can refer to the stored procedure.This provides better overall performance because the query has to beparsed only once, and less information needs to be sent between theserver and the client. You can also raise the conceptual level by havinglibraries of functions in the server. However, stored procedures ofcourse do increase the load on the database server system, as more of the work is done on the server side and less on the client (application)side.Triggers will also be implemented. A trigger is effectively a type of stored procedure, one that is invoked when a particular event occurs.For example, you can install a stored procedure that is triggered each time a record is deleted from a transaction table and that stored procedure automatically deletes the corresponding customer from a customer table when all his transactions are deleted.Indexes are used to find rows with specific column values quickly.Without an index, MySQL must begin with the first row and then read through the entire table to find the relevant rows. The larger the table, the more this costs. If the table has an index for the columns in question, MySQL can quickly determine the position to seek to in the middle of the data file without having to look at all the data. If a table has 1,000 rows, this is at least 100 times faster than reading sequentially. If you need to access most of the rows, it is faster to read sequentially, because this minimizes disk seeks.

Question : What is the maximum length of a table name, database name and field name in MySQL?

Answer : The following table describes the maximum length for each type of identifier.

Identifier	Maximum Length(bytes)
Database	64
Table	64
Column	64
Index	64
Alias	255

There are some restrictions on the characters that may appear in identifiers.

Question : How many values can the SET function of MySQL take?

Answer : MySQL set can take zero or more values but at the maximum it can take 64 values.

Question : What are the other commands to know the structure of table using MySQL commands except explain command?

Answer : describe Table-Name;

Question : How many tables will create when we create table, what are they?

Answer : The ‘.frm’ file stores the table definition.The data file has a ‘.MYD’ (MYData) extension.The index file has a ‘.MYI’ (MYIndex) extension.

Question : What is the purpose of the following files having extensions 1) .frm2) .myd 3) .myi? What do these files contain?

Answer : In MySql, the default table type is MyISAM.Each MyISAM table is stored on disk in three files. The files have names that begin with the table name and have an extension to indicate the file type.The ‘.frm’ file stores the table definition.The data file has a ‘.MYD’ (MYData) extension.The index file has a ‘.MYI’ (MYIndex) extension.

Question : What is maximum size of a database in MySQL?

Answer : If the operating system or file system places a limit on the number of files in a directory, MySQL is bound by that constraint.The efficiency of the operating system in handling large numbers offiles in a directory can place a practical limit on the number of tables in a database. If the time required to open a file in the directory increases significantly as the number of files increases, database performance can be adversely affected.The amount of available disk space limits the number of tables.MySQL 3.22 had a 4GB (4 gigabyte) limit on table size. With the MyISAM storage engine in MySQL 3.23, the maximum table size was increased to65536 terabytes (2567 – 1 bytes). With this larger allowed table size,the maximum effective table size for MySQL databases is usually determined by operating system constraints on file sizes, not by MySQL internal limits.The InnoDB storage engine maintains InnoDB tables within a table space that can be created from several files. This allows a table to exceed the maximum individual file size. The table space can include raw disk partitions, which allows extremely large tables. The maximum table space size is 64TB.The following table lists some examples of operating system file-size limits. This is only a rough guide and is not intended to be definitive.For the most up-to-date information, be sure to check the documentationspecific to your operating system.Operating System File-size Limit Linux 2.2-Intel 32-bit 2GB (LFS: 4GB)
Linux 2.4+ (using ext3 filesystem) 4TB
Solaris 9/10 16TB
NetWare w/NSS filesystem 8TB
Win32 w/ FAT/FAT32 2GB/4GB
Win32 w/ NTFS 2TB (possibly larger)
MacOS X w/ HFS+ 2TB

Question : Give the syntax of Grant and Revoke commands?

Answer : The generic syntax for grant is as following :
> GRANT [rights] on [database/s] TO [username@hostname] IDENTIFIED BY[password]now rights can be a) All privileges b) combination of create, drop, select, insert, update and delete etc. We can grant rights on all databse by using *.* or some specificdatabase by database.* or a specific table by database.table_name username@hotsname can be either username@localhost, username@hostname and username@% where hostname is any valid hostname and % represents any name, the *.*any condition password is simply the password of user.
The generic syntax for revoke is as following :
> REVOKE [rights] on [database/s] FROM [username@hostname] now rights can be as explained above a) All privileges b) combination of create, drop, select, insert, update and delete etc.username@hotsname can be either username@localhost, username@hostname and username@% where hostname is any valid hostname and % represents any name, the *.*any condition

Question : Explain Normalization concept?

Answer : The normalization process involves getting our data to conform to three progressive normal forms, and a higher level of normalization cannot be achieved until the previous levels have been achieved (there are actually five normal forms, but the last two are mainly academic and will not be discussed).First Normal Form  The First Normal Form (or 1NF) involves removal of redundant data from horizontal rows. We want to ensure that there is no duplication of data in a given row, and that every column stores the least amount of information possible (making the field atomic). Second Normal Form Where the First Normal Form deals with redundancy of data across a horizontal row, Second Normal Form (or 2NF) deals with redundancy of data in vertical columns. As stated earlier, the normal forms are progressive, so to achieve Second Normal Form, your tables must already be in First Normal Form.Third Normal Form I have a confession to make; I do not often use Third Normal Form. In Third Normal Form we are looking for data in our tables that is not fully dependent on the primary key, but dependent on another value in the table.

Question : How can we find the number of rows in a table using MySQL?

Answer : Use this for mysql>SELECT COUNT(*) FROM table_name;

Question : How can we find the number of rows in a result set using PHP?

Answer :
$result = mysql_query($sql, $db_link);
$num_rows = mysql_num_rows($result);
echo “$num_rows rows found”;

Question : How many ways we can we find the current date using MySQL?

Answer :
SELECT CURDATE();
CURRENT_DATE() = CURDATE()
for time use SELECT CURTIME();
CURRENT_TIME() = CURTIME()

Question : What are the advantages and disadvantages of Cascading Style Sheets?

Answer :
External Style Sheets
Advantages : Can control styles for multiple documents at once. Classes can be created for use on multiple HTML element types in many documents.Selector and grouping methods can be used to apply styles under complex contexts.
Disadvantages : An extra download is required to import style information for eachdocument The rendering of the document may be delayed until the externalstyle sheet is loaded becomes slightly unwieldy for small quantities ofstyle definitions.
Embedded Style Sheets
Advantages : Classes can be created for use on multiple tag types in the document.Selector and grouping methods can be used to apply styles under complexcontexts. No additional downloads necessary to receive style information.
Disadvantages : This method can not control styles for multiple documents at once.
Inline Styles
Advantages : Useful for small quantities of style definitions. Can override otherstyle specification methods at the local level so only exceptions needto be listed in conjunction with other style methods.
Disadvantages : Does not distance style information from content (a main goal ofSGML/HTML). Can not control styles for multiple documents at once.Author can not create or control classes of elements to control multipleelement types within the document. Selector grouping methods can not beused to create complex element addressing scenarios

Question : What type of inheritance that PHP supports?

Answer : In PHP an extended class is always dependent on a single base class,that is, multiple inheritance is supported by interfaces. Classes are extended using the keyword ‘extends’.

Question : What is the difference between Primary Key and Unique key?

Answer : Primary Key: A column in a table whose values uniquely identify therows in the table. A primary key value cannot be NULL. Unique Key: Unique Keys are used to uniquely identify each row in thetable. There can be one and only one row for each unique key value. So NULL can be a unique key.There can be only one primary key for a table but there can be morethan one unique for a table.

Question : The structure of table view buyers is as follows:

Field	Type	Null	Key	Default	Extra
user_pri_id	int(15)		PRI	null	auto_increment
userid	varchar(10)	YES		null

the value of user_pri_id the last row 999 then What will happen inthe following conditions?Condition1: Delete all the rows and insert another row then.What is the starting value for this auto incremented field user_pri_id ,Condition2: Delete the last row(having the field value 999) andinsert another row then. What is the value for this auto incremented field user_pri_id.

Answer : In both cases let the value for auto increment field be n then nextrow will have value n+1 i.e. 1000.

Question : What are the advantages/disadvantages of MySQL and PHP?

Answer : Both of them are open source software (so free of cost), supportcross platform. php is faster then ASP and JSP.

Question : What is the difference between GROUP BY and ORDER BY in Sql?

Answer : ORDER BY [col1],[col2],…,[coln]; Tells DBMS according to what columns it should sort the result. If two rows will have the same value in col1it will try to sort them according to col2 and so on.GROUP BY[col1],[col2],…,[coln]; Tells DBMS to group results with same value of column col1. You can use COUNT(col1), SUM(col1), AVG(col1) with it, if you want to count all items in group, sum all values or view average.

Question : What is the difference between char and varchar data types?

Answer : Set char to occupy n bytes and it will take n bytes even if u r storing a value of n-m bytes Set varchar to occupy n bytes and it will take only the required space and will not use the n bytes eg. name char(15) will waste 10 bytes if we store ‘mizan’, if each char takes a byte eg. name varchar(15) will just use 5 bytes if we store ‘mizan’, if each char takes a byte. rest 10 bytes will be free.

Question : What is the functionality of md5 function in PHP?

Answer : Calculate the md5 hash of a string. The hash is a 32-characterhexadecimal number. I use it to generate keys which I use to identifyusers etc. If I add random no techniques to it the md5 generated nowwill be totally different for the same string I am using.

Question : How can I load data from a text file into a table?

Answer : you can use LOAD DATA INFILE file_name; syntax to load datafrom a text file. but you have to make sure thata) data is delimitedb) columns and data matched correctly.

Question : How can we know the number of days between two given dates using MySQL?

Answer : SELECT DATEDIFF(’2007-03-07?,’2005-01-01?);

Question : How can we know the number of days between two given dates using PHP?

Answer : $date1 = date(’Y-m-d’);
$date2 = ‘2006-08-15?;
$days = (strtotime($date1) – strtotime($date2)) / (60 * 60 * 24);

PHP OOPS Interview Questions & Answers

1) Explain what is object oriented programming language?
Object oriented programming language allows concepts such as modularity, encapsulation, polymorphism and inheritance.  Objects are said to be the most important part of object oriented language. Concept revolves around making simulation programs around an object. Organize a program around its data (object)& set well define interface to that data. i.e. objects and a set of well defined interfaces to that data. OOP is the common abbreviation for Object-Oriented Programming.  OOps have many properties such as DataHiding,Inheritence,Data Absraction,Data Encapsulation and many more.

2) Name some languages which have object oriented language and characteristics?
Some of the languages which have object oriented languages present in them are ABAP, ECMA Script, C++, Perl, LISP, C#, Tcl, VB, Ruby, Python, PHP, etc. Popularity of these languages has increased considerably as they can solve complex problems with ease.
3) Explain about UML?
UML or unified modeling language is regarded to implement complete specifications and features of object oriented language. Abstract design can be implemented in object oriented programming languages. It lacks implementation of polymorphism on message arguments which is a OOPs feature.
4) Explain the meaning of object in object oriented programming?
Languages which are called as object oriented almost implement everything in them as objects such as punctuations, characters, prototypes, classes, modules, blocks, etc. They were designed to facilitate and implement object oriented methods.
5) Explain about message passing in object oriented programming?
Message passing is a method by which an object sends data to another object or requests other object to invoke method. This is also known as interfacing. It acts like a messenger from one object to other object to convey specific instructions.
6) State about Java and its relation to Object oriented programming?
Java is widely used and its share is increasing considerably which is partly due to its close resemblance to object oriented languages such as C++. Code written in Java can be transported to many different platforms without changing it. It implements virtual machine.
7) What are the problems faced by the developer using object oriented programming language?

These are some of the problems faced by the developer using object oriented language they are: –

a) Object oriented uses design patterns which can be referred to as anything in general.
b) Repeatable solution to a problem can cause concern and disagreements and it is one of the major problems in software design.
8 ) State some of the advantages of object oriented programming?
Some of the advantages of object oriented programming are as follows: –
a) A clear modular structure can be obtained which can be used as a prototype and it will not reveal the mechanism behind the design. It does have a clear interface.
b) Ease of maintenance and modification to the existing objects can be done with ease.
c) A good framework is provided which facilitates in creating rich GUI applications.
9 ) Explain about inheritance in OOPS?
Objects in one class can acquire properties of the objects in other classes by way of inheritance. Reusability which is a major factor is provided in object oriented programming which adds features to a class without modifying it. New class can be obtained from a class which is already present.
10) Explain about the relationship between object oriented programming and databases?
Object oriented programming and relational database programming are almost similar in software engineering. RDBMS will not store objects directly and that’s where object oriented programming comes into play. Object relational mapping is one such solution.
11) Explain about a class in OOP?
In Object oriented programming usage of class often occurs. A class defines the characteristics of an object and its behaviors. This defines the nature and functioning of a specified object to which it is assigned. Code for a class should be encapsulated.

12) Explain the usage of encapsulation?
Encapsulation specifies the different classes which can use the members of an object. The main goal of encapsulation is to provide an interface to clients which decrease the dependency on those features and parts which are likely to change in future. This facilitates easy changes to the code and features.
13) Explain about abstraction?
Abstraction can also be achieved through composition. It solves a complex problem by defining only those classes which are relevant to the problem and not involving the whole complex code into play.
14) Explain what a method is?
A method will affect only a particular object to which it is specified. Methods are verbs meaning they define actions which a particular object will perform. It also defines various other characteristics of a particular object.
15) Name the different Creational patterns in OO design?
There are three patterns of design out of which Creational patterns play an important role the various patterns described underneath this are: –
a) Factory pattern
b) Single ton pattern
c) Prototype pattern
d) Abstract factory pattern
e) Builder pattern
16) Explain about realistic modeling?
As we live in a world of objects, it logically follows that the object oriented approach models the real world accurately. The object oriented approach allows you to identify entities as objects having attributes and behavior.
17) Explain about the analysis phase?
The anlaysis or the object oriented analysis phase considers the system as a solution to a problem in its environment or domain. Developer concentrates on obtaining as much information as possible about the problem. Critical requirements needs to be identified.

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1) Explain the rationale behind Object Oriented concepts?

Object oriented concepts form the base of all modern programming languages. Understanding the basic concepts of object-orientation helps a developer to use various modern day programming languages, more effectively.
2) Explain about Object oriented programming?
Object oriented programming is one of the most popular methodologies in software development. It offers a powerful model for creating computer programs. It speeds the program development process, improves maintenance and enhances reusability of programs.
3) Explain what is an object?
An object is a combination of messages and data. Objects can receive and send messages and use messages to interact with each other. The messages contain information that is to be passed to the recipient object.
4) Explain the implementation phase with respect to OOP?
The design phase is followed by OOP, which is the implementation phase. OOP provides specifications for writing programs in a programming language. During the implementation phase, programming is done as per the requirements gathered during the analysis and design phases.
5) Explain about the Design Phase?
In the design phase, the developers of the system document their understanding of the system. Design generates the blue print of the system that is to be implemented. The first step in creating an object oriented design is the identification of classes and their relationships.
6) Explain about a class?
Class describes the nature of a particular thing. Structure and modularity is provided by a Class in object oriented programming environment. Characteristics of the class should be understandable by an ordinary non programmer and it should also convey the meaning of the problem statement to him. Class acts like a blue print.

7) Explain about instance in object oriented programming?
Every class and an object have an instance. Instance of a particular object is created at runtime. Values defined for a particular object define its State. Instance of an object explains the relation ship between different elements.
8 ) Explain about inheritance?
Inheritance revolves around the concept of inheriting knowledge and class attributes from the parent class. In general sense a sub class tries to acquire characteristics from a parent class and they can also have their own characteristics. Inheritance forms an important concept in object oriented programming.
9) Explain about multiple inheritance?
Inheritance involves inheriting characteristics from its parents also they can have their own characteristics. In multiple inheritance a class can have characteristics from multiple parents or classes. A sub class can have characteristics from multiple parents and still can have its own characteristics.
10) Explain about encapsulation?
Encapsulation passes the message without revealing the exact functional details of the class. It allows only the relevant information to the user without revealing the functional mechanism through which a particular class had functioned.
11) Explain about abstraction?
Abstraction simplifies a complex problem to a simpler problem by specifying and modeling the class to the relevant problem scenario. It simplifies the problem by giving the class its specific class of inheritance. Composition also helps in solving the problem to an extent.
12) Explain the mechanism of composition?
Composition helps to simplify a complex problem into an easier problem. It makes different classes and objects to interact with each other thus making the problem to be solved automatically. It interacts with the problem by making different classes and objects to send a message to each other.
13) Explain about polymorphism?
Polymorphism helps a sub class to behave like a parent class. When an object belonging to different data types respond to methods which have a same name, the only condition being that those methods should perform different function.
14) Explain about overriding polymorphism?
Overriding polymorphism is known to occur when a data type can perform different functions. For example an addition operator can perform different functions such as addition, float addition etc. Overriding polymorphism is generally used in complex projects where the use of a parameter is more.
15) Explain about object oriented databases?
Object oriented databases are very popular such as relational database management systems. Object oriented databases systems use specific structure through which they extract data and they combine the data for a specific output. These DBMS use object oriented languages to make the process easier.
16) Explain about parametric polymorphism?
Parametric polymorphism is supported by many object oriented languages and they are very important for object oriented techniques. In parametric polymorphism code is written without any specification for the type of data present. Hence it can be used any number of times.
17) What are all the languages which support OOP?
There are several programming languages which are implementing OOP because of its close proximity to solve real life problems. Languages such as Python, Ruby, Ruby on rails, Perl, PHP, Coldfusion, etc use OOP. Still many languages prefer to use DOM based languages due to the ease in coding.

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