session_destroy

(PHP 4, PHP 5)

session_destroy — 销毁一个会话中的全部数据

说明

bool session_destroy ( void )

session_destroy() 销毁当前会话中的全部数据，但是不会重置当前会话所关联的全局变量，也不会重置会话 cookie。如果需要再次使用会话变量，必须重新调用 session_start() 函数。

为了彻底销毁会话，比如在用户退出登录的时候，必须同时重置会话 ID。如果是通过 cookie 方式传送会话 ID 的，那么同时也需要调用 setcookie() 函数来删除客户端的会话 cookie。

返回值

成功时返回 TRUE ，或者在失败时返回 FALSE 。

范例

Example #1 销毁会话数据以及 $_SESSION

  <?php
 // 初始化会话。
// 如果要使用会话，别忘了现在就调用：
 session_start ();

 // 重置会话中的所有变量
 $_SESSION  = array();

 // 如果要清理的更彻底，那么同时删除会话 cookie
// 注意：这样不但销毁了会话中的数据，还同时销毁了会话本身
 if ( ini_get ( "session.use_cookies" )) {
     $params  =  session_get_cookie_params ();
     setcookie ( session_name (),  '' ,  time () -  42000 ,
         $params [ "path" ],  $params [ "domain" ],
         $params [ "secure" ],  $params [ "httponly" ]
    );
}

 // 最后，销毁会话
 session_destroy ();
 ?>

注释

Note:

对于旧版本中不使用 $_SESSION 的代码，仅能使用 session_unset() 来完成会话销毁工作。

参见

unset() - 释放给定的变量
setcookie() - Send a cookie

用户评论:

[#1] Jack Luo [2014-03-27 10:08:13]

It took me a while to figure out how to destroy a particular session in php. Note I'm not sure if solution provided below is perfect but it seems work for me. Please feel free to post any easier way to destroy a particular session. Because it's quite useful for functionality of force an user offline.

1. If you're using db or memcached to manage session, you can always delete that session entry directly from db or memcached.

2. Using generic php session methods to delete a particular session(by session id).

<?php $session_id_to_destroy = 'nill2if998vhplq9f3pj08vjb1'; // 1. commit session if it's started. if (session_id()) { session_commit(); } // 2. store current session id session_start(); $current_session_id = session_id(); session_commit(); // 3. hijack then destroy session specified. session_id($session_id_to_destroy); session_start(); session_destroy(); session_commit(); // 4. restore current session id. If don't restore it, your current session will refer to the session you just destroyed! session_id($current_session_id); session_start(); session_commit(); ?>

[#2] luqui at yahoo dot com [2013-09-27 12:25:42]

If you want to destroy the session when it starts, don't forget to declare the session with your code because when you do that this will ensure that your session will be more effective. This also enhances the effieciency of you code.

[#3] Praveen V [2012-09-14 04:39:57]

If you want to change the session id on each log in, make sure to use session_regenerate_id(true) during the log in process.

<?php session_start(); session_regenerate_id(true); ?>

[Edited by moderator (googleguy at php dot net)]

[#4] administrator at anorhack dot com [2007-08-01 07:34:46]

Destroying a session from a background job

I have a thief-protection system that compares country codes from login IPs via whois. This has to run in the background as it is way too processor-hungry to be run in the browser.

What I needed was a way to destroy the web session from the background job. For some reason, a background session_destroy APPEARS to work, but doesnt't actually destroy the web session.

There is a work around, I set the username to NULL and the web code picks up on that, bouncing the user (thief) to a "gotcha" page where his IP is logged.

Yes I know its nasty and dirty, but surprisingly it works.

$sid = the session_id() of the suspicious web session, passed in $argv to the background job

The trick is to "stuff" the $_GET array with the sid, then the session_start in the background job picks this value up (as if it were a genuine trans-sid type thing...?PHPSESSID=blah) and "connects to" the web session. All $_SESSION variable can be viewed (and CHANGED , which is how this kludge works) but for some reason (that no doubt someone will illuminate) they can't be unset...setting the particular variable to NULL works well though:

$_GET[session_name()]=$sid;
session_start();
// prove we are getting the web session data
foreach($_SESSION as $k => $v) echo($k."=".$v);
// now kill the thief
$_SESSION['username']=NULL;
//web session variable now NULL - honestly!

[#5] Colin [2007-02-07 01:52:15]

Note that when you are using a custom session handler, session_destroy will cause a fatal error if you have set the session destroy function used by session_set_save_handler to private.

Example:
Fatal error: Call to private method Session::sessDestroy()

where sessDestroy was the function I specified in the 5th parameter of session_set_save_handler.

Even though it isn't all that desirable, the simple solution is to set sessDestroy to public.