PHP Sessions

A session is a global variable stored on the server.

As we know HTTP is a stateless protocol, when a user requests one page, followed by another, HTTP does not provide a way for you to tell that both requests came from the same user.

The idea of session control is to be able to track a user during a single session on a website. It helps us in storing the user information to be used across multiple pages.

If you can do this, you can easily support logging in a user and showing content according to her authorization level or personal preferences. You can track the user's behavior, and you can implement shopping cards.

Starting a Session

In PHP, the session_start() function is used to create a client session and generate a session id. Once the session has been created, we can create any number of session variables. The session variable is created in key-value pairs.

Examples

<?php
	session_start();
	$_SESSION['userid'] = '';
	$_SESSION['department'] = '';
?>	

The session_start() takes no argument and causes PHP either to notice a session id that has been passed to it or create a new session id if not found. In PHP, $_SESSION is an associative array that contains all session variables.





PHP Unset Session Variable

The session_unset() function is used to free all variables in the session. It takes no arguments.

Examples

<?php
	// remove all session variables
	session_unset();
?>	

Destroy a PHP Session

The session_destory() function is used to get rid of all session variables information that has been stored. It does not unset any variables in the current script or the session cookie.

Examples

<?php
	//destroy entire session 
	session_destroy();
?>	

We can use the unset() function, if you want to destroy only a session single item.

<?php
	//destroy only department session 
	unset($_SESSION['department']); 
?>	





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