CascadiaPHP 2024

session_unset

(PHP 4, PHP 5, PHP 7, PHP 8)

session_unsetFree all session variables

Description

session_unset(): bool

The session_unset() function frees all session variables currently registered.

Parameters

This function has no parameters.

Return Values

Returns true on success or false on failure.

Changelog

Version Description
7.2.0 The return type of this function is bool now. Formerly, it has been void.

Notes

Note:

If $_SESSION is used, use unset() to unregister a session variable, i.e. unset($_SESSION['varname']);.

Caution

Do NOT unset the whole $_SESSION with unset($_SESSION) as this will disable the registering of session variables through the $_SESSION superglobal.

Note:

The use of session_unset() is identical to $_SESSION = [].

Caution

This function works only if a session is active. It will not clear the $_SESSION array if the session has not been started yet or has already been destroyed. Use $_SESSION = [] to unset all session variables even if the session is not active.

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User Contributed Notes 5 notes

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39
tim at leethost dot com
12 years ago
I was having a problem clearing all session variables, deleting the session, and creating a new session without leaving old session stuff behind in all browsers. The below code is perfect for a logout script to totally delete everything and start new. It even works in Chrome which seems to not work as other browsers when trying do logout and start a new session.

<?php
session_start
();
session_unset();
session_destroy();
session_write_close();
setcookie(session_name(),'',0,'/');
session_regenerate_id(true);
?>
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25
jerry
8 years ago
The difference between both session_unset and session_destroy is as follows:

session_unset just clears out the session for usage. The session is still on the users computer. Note that by using session_unset, the variable still exists. session_unset just remove all session variables. it does not destroy the session....so the session would still be active.

Using session_unset in tandem with session_destroy however, is a much more effective means of actually clearing out data. As stated in the example above, this works very well, cross browser. session_destroy is destroy the session. session_destroy() to kill all session information.....This is the more secure function to use.
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0
christian+php at
16 days ago
The solution provided by tim at leethost dot com is nice but you must check a active session first, because else you fill the logs with PHP Errors or Notices depending on your settings. I use it as a function, and it works smooth.

```php
/** @return void */
public static function sayonara():void
{
if (session_status() !== PHP_SESSION_ACTIVE) :void
{
session_start();
session_unset();
session_destroy();
session_write_close();
setcookie(session_name(), '', 0, '/');
session_regenerate_id(true);
}
}

sayonara();
```
up
-18
Jeroen
19 years ago
note to Jason: I don't know the exact mechanics of it (since I'm quite new to sessions) but I think you need to use session_unset() BEFORE you can use session_destroy() at all. I thought that session_unset() was for scripted variables, and session_destroy() just for anything saved on your side regarding the session.
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-22
zach at zkwarta dot com
19 years ago
The difference between both session_unset and session_destroy is as follows:

session_unset just clears out the sesison for usage. The session is still on the users computer. Note that by using session_unset, the variable still exists.

Using session_unset in tandem with session_destroy however, is a much more effective means of actually clearing out data. As stated in the example above, this works very well, cross browser:

session_unset();
session_destroy();

I noticed that in firefox, one could simply use sesison_unset and the session would be cleared. When trying this on IE, I was horrified to find out that the data was still there, so I had to use session destroy.
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