PHP Interview Questions

PHP Interview Question And Answers:

Q.What is PHP?

PHP is a server side scripting language commonly used for web applications. PHP has many frameworks and cms for creating websites.Even a non technical person can cretae sites using its CMS.WordPress,osCommerce are the famus CMS of php.It is also an object oriented programming language like java,C-sharp etc.It is very eazy for learning

Q.What is the use of “echo” in php?

It is used to print a data in the webpage, Example: <?php echo ‘Car insurance’; ?> , The following code print the text in the webpage

Q.How to include a file to a php page?

We can include a file using “include() ” or “require()” function with file path as its parameter.

Q.What’s the difference between include and require?

If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.

Q.require_once(), require(), include().What is difference between them?

require() includes and evaluates a specific file, while require_once() does that only if it has not been included before (on the same page). So, require_once() is recommended to use when you want to include a file where you have a lot of functions for example. This way you make sure you don’t include the file more times and you will not get the “function re-declared” error.

Q.Differences between GET and POST methods ?

We can send 1024 bytes using GET method but POST method can transfer large amount of data and POST is the secure method than GET method .

Q.How to declare an array in php?

Eg : var $arr = array(‘apple’, ‘grape’, ‘lemon’);

Q.What is the use of ‘print’ in php?

This is not actually a real function, It is a language construct. So you can use with out parentheses with its argument list.
Example print(‘PHP Interview questions’); 
print ‘Job Interview ‘);

Q.What is use of in_array() function in php ?

in_array used to checks if a value exists in an array

What is use of count() function in php ?

count() is used to count all elements in an array, or something in an object

Q.What’s the difference between include and require?

It’s how they handle failures. If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.

Q.What is the difference between Session and Cookie?

The main difference between sessions and cookies is that sessions are stored on the server, and cookies are stored on the user’s computers in the text file format. Cookies can not hold multiple variables,But Session can hold multiple variables.We can set expiry for a cookie,The session only remains active as long as the browser is open.Users do not have access to the data you stored in Session,Since it is stored in the server.Session is mainly used for login/logout purpose while cookies using for user activity tracking

Q.How to set cookies in PHP?

Setcookie(“sample”, “ram”, time()+3600);

Q.How to Retrieve a Cookie Value?

eg : echo $_COOKIE[“user”];

Q.How to create a session? How to set a value in session ? How to Remove data from a session?

Create session : session_start();
Set value into session : $_SESSION[‘USER_ID’]=1;
Remove data from a session : unset($_SESSION[‘USER_ID’];

Q.what types of loops exist in php?

for,while,do while and foreach (NB: You should learn its usage)

Q.How to create a mysql connection?


Q.How to select a database?


Q.How to execute an sql query? How to fetch its result ?

$my_qry = mysql_query(“SELECT * FROM `users` WHERE `u_id`=’1′; “); 
$result = mysql_fetch_array($my_qry);
echo $result[‘First_name’];

Q.Write a program using while loop

$my_qry = mysql_query(“SELECT * FROM `users` WHERE `u_id`=’1′; “); 
while($result = mysql_fetch_array($my_qry))
echo $result[‘First_name’.].”<br/>”;

Q.How we can retrieve the data in the result set of MySQL using PHP?

  • mysql_fetch_row
  • mysql_fetch_array
  • mysql_fetch_object
  • mysql_fetch_assoc

Q.What is the use of explode() function ?

Syntax : array explode ( string $delimiter , string $string [, int $limit ] ); 
This function breaks a string into an array. Each of the array elements is a substring of string formed by splitting it on boundaries formed by the string delimiter.

Q.What is the difference between explode() and split() functions?

Split function splits string into array by regular expression. Explode splits a string into array by string.

Q.How to redirect a page in php?

The following code can be used for it, header(“Location:index.php”);

Q.How stop the execution of a php scrip ?

exit() function is used to stop the execution of a page

Q.How to set a page as a home page in a php based site ?

index.php is the default name of the home page in php based sites

Q.What is the difference between mysql_fetch_array() and mysql_fetch_assoc() ?

mysql_fetch_assoc function Fetch a result row as an associative array, Whilemysql_fetch_array() fetches an associative array, a numeric array, or both

Q.What is the importance of “method” attribute in a html form?

“method” attribute determines how to send the form-data into the server.There are two methods, get and post. The default method is get.This sends the form information by appending it on the URL.Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.

Q.What is the importance of “action” attribute in a html form?

The action attribute determines where to send the form-data in the form submission.

Q.What is the use of “enctype” attribute in a html form?

The enctype attribute determines how the form-data should be encoded when submitting it to the server. We need to set enctype as “multipart/form-data”when we are using a form for uploading files

Q.Define Object-Oriented Methodology

Object orientation is a software/Web development methodology that is based on the modeling a real world system.An object is the core concept involved in the object orientation. An object is the copy of the real world enity.An object oriented model is a collection of objects and its inter-relationships

Q.How do you define a constant?

Using define() directive, like define (“MYCONSTANT”,150)

Q.Difference between mysql_connect and mysql_pconnect?

There is a good page in the php manual on the subject, in short mysql_pconnect() makes a persistent connection to the database which means a SQL link that do not close when the execution of your script ends. mysql_connect()provides only for the databasenewconnection while using mysql_pconnect , the function would first try to find a (persistent) link that’s already open with the same host, username and password. If one is found, an identifier for it will be returned instead of opening a new connection… the connection to the SQL server will not be closed when the execution of the script ends. Instead, the link will remain open for future use.

Q.What is the use of “ksort” in php?

It is used for sort an array by key in reverse order.

Q.What is the difference between $var and $$var?

They are both variables. But $var is a variable with a fixed name. $$var is a variable who’s name is stored in $var. For example, if $var contains “message”, $$var is the same as $message.

Q.What are the different types of errors in PHP ?

Here are three basic types of runtime errors in PHP:

  • 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 behavior.
  • 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.
  • 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.What is PEAR?

PEAR is a framework and distribution system for reusable PHP components.The project seeks to provide a structured library of code, maintain a system for distributing code and for managing code packages, and promote a standard coding style.PEAR is broken into three classes: PEAR Core Components, PEAR Packages, and PECL Packages. The Core Components include the base classes of PEAR and PEAR_Error, along with database, HTTP, logging, and e-mailing functions. The PEAR Packages include functionality providing for authentication, networking, and file system features, as well as tools for working with XML and HTML templates.

Q.Distinguish between urlencode and urldecode?

This method is best when encode a string to used in a query part of a url. it returns a string in which all non-alphanumeric characters except -_. have replece with a percentege(%) sign . the urldecode->Decodes url to encode string as any %and other symbole are decode by the use of the urldecode() function.

Q.What are the different errors in PHP?

In PHP, there are three types of runtime errors, they are:

These are important errors. Example: When we try to include () file which is not available. These errors are showed to the user by default but they will not result in ending the script. 
These errors are non-critical and trivial errors that come across while executing the script in PHP. Example: trying to gain access the variable which is not defined. These errors are not showed to the users by default even if the default behavior is changed. 
Fatal errors: 
These are critical errors. Example: instantiating an object of a class which does not exist or a non-existent function is called. These errors results in termination of the script immediately and default behavior of PHP is shown to them when they take place. Twelve different error types are used to represent these variations internally.

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