Unset all session in php

session_destroy

session_destroy() destroys all of the data associated with the current session. It does not unset any of the global variables associated with the session, or unset the session cookie. To use the session variables again, session_start() has to be called.

Note: You do not have to call session_destroy() from usual code. Cleanup $_SESSION array rather than destroying session data.

In order to kill the session altogether, the session ID must also be unset. If a cookie is used to propagate the session ID (default behavior), then the session cookie must be deleted. setcookie() may be used for that.

When session.use_strict_mode is enabled. You do not have to remove obsolete session ID cookie because session module will not accept session ID cookie when there is no data associated to the session ID and set new session ID cookie. Enabling session.use_strict_mode is recommended for all sites.

Immediate session deletion may cause unwanted results. When there is concurrent requests, other connections may see sudden session data loss. e.g. Requests from JavaScript and/or requests from URL links.

Although current session module does not accept empty session ID cookie, but immediate session deletion may result in empty session ID cookie due to client(browser) side race condition. This will result that the client creates many session ID needlessly.

To avoid these, you must set deletion time-stamp to $_SESSION and reject access while later. Or make sure your application does not have concurrent requests. This applies to session_regenerate_id() also.

Parameters

This function has no parameters.

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session_unset

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

Notes

Note:

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

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 = [] .

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.

User Contributed Notes 4 notes

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.

session_start ();
session_unset ();
session_destroy ();
session_write_close ();
setcookie ( session_name (), » , 0 , ‘/’ );
session_regenerate_id ( true );
?>

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.

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.

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:

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.

• Session Functions
  • session_​abort
  • session_​cache_​expire
  • session_​cache_​limiter
  • session_​commit
  • session_​create_​id
  • session_​decode
  • session_​destroy
  • session_​encode
  • session_​gc
  • session_​get_​cookie_​params
  • session_​id
  • session_​module_​name
  • session_​name
  • session_​regenerate_​id
  • session_​register_​shutdown
  • session_​reset
  • session_​save_​path
  • session_​set_​cookie_​params
  • session_​set_​save_​handler
  • session_​start
  • session_​status
  • session_​unset
  • session_​write_​close

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  Функции для работы с сессиями

  Be aware of the fact that absolute URLs are NOT automatically rewritten to contain the SID.

  Of course, it says so in the documentation (‘Passing the Session Id’) and of course it makes perfectly sense to have that restriction, but here’s what happened to me:
  I have been using sessions for quite a while without problems. When I used a global configuration file to be included in all my scripts, it contained a line like this:

  which was used to make sure that all automatically generated links had the right prefix (just like $cfg[‘PmaAbsoluteUri’] works in phpMyAdmin). After introducing that variable, no link would pass the SID anymore, causing every script to return to the login page. It took me hours (!!) to recognize that this wasn’t a bug in my code or some misconfiguration in php.ini and then still some more time to find out what it was. The above restriction had completely slipped from my mind (if it ever was there. )

  Skipping the ‘http:’ did the job.

  OK, it was my own mistake, of course, but it just shows you how easily one can sabotage his own work for hours. Just don’t do it 😉

  Sessions and browser’s tabs

  May you have noticed when you open your website in two or more tabs in Firefox, Opera, IE 7.0 or use ‘Control+N’ in IE 6.0 to open a new window, it is using the same cookie or is passing the same session id, so the another tab is just a copy of the previous tab. What you do in one will affect the another and vice-versa. Even if you open Firefox again, it will use the same cookie of the previous session. But that is not what you need mostly of time, specially when you want to copy information from one place to another in your web application. This occurs because the default session name is «PHPSESSID» and all tabs will use it. There is a workaround and it rely only on changing the session’s name.

  Put these lines in the top of your main script (the script that call the subscripts) or on top of each script you have:

  if( version_compare ( phpversion (), ‘4.3.0’ )>= 0 ) <
  if(! ereg ( ‘^SESS1+$’ , $_REQUEST [ ‘SESSION_NAME’ ])) <
  $_REQUEST [ ‘SESSION_NAME’ ]= ‘SESS’ . uniqid ( » );
  >
  output_add_rewrite_var ( ‘SESSION_NAME’ , $_REQUEST [ ‘SESSION_NAME’ ]);
  session_name ( $_REQUEST [ ‘SESSION_NAME’ ]);
  >
  ?>

  How it works:

  First we compare if the PHP version is at least 4.3.0 (the function output_add_rewrite_var() is not available before this release).

  After we check if the SESSION_NAME element in $_REQUEST array is a valid string in the format «SESSIONxxxxx», where xxxxx is an unique id, generated by the script. If SESSION_NAME is not valid (ie. not set yet), we set a value to it.

  uniqid(») will generate an unique id for a new session name. It don’t need to be too strong like uniqid(rand(),TRUE), because all security rely in the session id, not in the session name. We only need here a different id for each session we open. Even getmypid() is enough to be used for this, but I don’t know if this may post a treat to the web server. I don’t think so.

  output_add_rewrite_var() will add automatically a pair of ‘SESSION_NAME=SESSxxxxx’ to each link and web form in your website. But to work properly, you will need to add it manually to any header(‘location’) and Javascript code you have, like this:

  The last function, session_name() will define the name of the actual session that the script will use.

  So, every link, form, header() and Javascript code will forward the SESSION_NAME value to the next script and it will know which is the session it must use. If none is given, it will generate a new one (and so, create a new session to a new tab).

  May you are asking why not use a cookie to pass the SESSION_NAME along with the session id instead. Well, the problem with cookie is that all tabs will share the same cookie to do it, and the sessions will mix anyway. Cookies will work partially if you set them in different paths and each cookie will be available in their own directories. But this will not make sessions in each tab completly separated from each other. Passing the session name through URL via GET and POST is the best way, I think.

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  PHP how to unset a session variable

  

  Posted on Sep 28, 2022

  There are three ways you can unset session variables in PHP:

  This tutorial will help you learn the methods mentioned above.

  Unset session variable with unset

  To unset your session variable in PHP, you need to call the unset construct and pass the $_SESSION variable as its parameter.

    en ) Although unset is a construct, you need to surround the parameters with round brackets.

  The unset construct allows you to unset multiple variables with one call as well:

    dark )  Using the unset construct you can remove parts of your session data selectively.

  Unset session variable with session_unset()

  If you want to clear the entire session, you can use either the session_unset() or session_destroy() function.

  The session_unset() function unset all your session variables:

     session_unset() immediately clears the session variables. It’s the same as assigning the $_SESSION variable to an empty array:

  This function doesn’t interrupt any concurrent requests that require access to the session.

  If you need to immediately clear the session from all requests to your server, you need to call the session_destroy() function.

  Unset session variable with session_destroy()

  session_destroy() destroys the session, so PHP will generate a new session id when you call session_start() again

  To get rid of the entire session, you also need to remove the session cookie as follows:

       PHP sessions are used to store information about your web application.

  Most of the time, you don’t want to clear the entire session data. The unset construct is the preferred way to remove session data.

  But if you have cases where you want to remove the session completely, then using the above example with session_destroy() should be the way to go.

  Now you’ve learned how to unset the session variable in PHP. Great! 👍

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