Session 函数
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session_unset

(PHP 4, PHP 5)

session_unset — Free all session variables

说明

void session_unset ( void )

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

返回值

没有返回值。

注释

Note:

If $_SESSION (or $HTTP_SESSION_VARS for PHP 4.0.6 or less) is used, use unset() to unregister a session variable, i.e. unset ($_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.

Session 函数
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PHP手册
PHP手册 - N: Free all session variables

用户评论:

tim at leethost dot com (05-Jan-2012 11:50)

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);
?>

notsonewbie (05-Jan-2011 11:56)

dash2nash: you have to start the session before you can unset or destroy it.

dash2nash (21-Oct-2010 02:16)

Im using chrome and Im not a pro in php, but Im certainly sure that session sure is buggy on google chrome, I use:

    session_unset();
    session_destroy();
    $_SESSION = array();
    session_start();

every time the page load, yet, some of the session still there. It's quite scary problem :s

angelitoestebancito at gmail dot com (16-Aug-2008 10:41)

If you create a logout.php to end user session, do not forget to start the session in this page!, using session_start() at the very begging of your script. Thus,

session_start();
session_unset();
session_destroy();

will be the right sequence to end a user's session.
This is a very basic concept, but took me a while to realize I was forgetting to start the session.

00 at f00n dot com (24-Jun-2008 03:00)

-------------------------------------------------------
InterNic
20-May-2006 11:20
sometimes you might have problems even if using both session_unset and session_destroy. You have to clear the $_SESSION array. I got it working this way:

session_unset();
session_destroy();
$_SESSION = array();
-------------------------------------------------------

When I used this method the session still existed in structure until the array is reset completely.

This, however, has the drawback of clearing all sessions which may not be ideal in some cases.

Named sessions may help in such cases.

pentek_i at inf dot elte dot hu (09-Aug-2006 12:54)

You should know that on recent PHP only the first one of these functions works correctly. And if you use the other two, var_dump will print you the result you expected (session cleaned up), but the session file on the server won't be cleaned up. So use the first one.

<?php

function session_clean1($logout=false)
 {
  $v=array();
  foreach($_SESSION as $x=>$y)
   if($x!="redirector"&&($x!="user"||$logout))
    $v[]=$x;

  foreach($v as $x)
   unset($_SESSION[$x]);
  return;
 }

function session_clean2($logout=false)
 {
  foreach($_SESSION as $x=>$y)
   if($x!="redirector"&&($x!="user"||$logout))
    unset($_SESSION[$x]);
  return;
 }

function session_clean3($logout=false)
 {
  $s=($logout||!isset($_SESSION["user"]))?array():
   array("user"=>$_SESSION["user"]);
  if(isset($_SESSION["redirector"]))
   $s["redirector"]=$_SESSION["redirector"];
  $_SESSION=$s;
 }

?>

On previous php (<<5.1.4) releases at least the third one worked correctly.

InterNic (20-May-2006 11:20)

sometimes you might have problems even if using both session_unset and session_destroy. You have to clear the $_SESSION array. I got it working this way:

session_unset();
session_destroy();
$_SESSION = array();

zach at zkwarta dot com (13-Jul-2005 11:32)

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.

Jeroen (15-Jan-2005 09:42)

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.

(21-Mar-2001 04:58)

To further clarify the note above... this can be done via the session handling directives in your php.ini file... there are options to set garbage collection probability (via percent... i.e. 75 means it would run 3 out of every 4 page accesses), and the amount of time a session object can remain active before the garbage collection process sees it as garbage.

dmertens at zyprexia dot com (31-Jan-2001 05:11)

The session files are automaticly deleted after the session-timeout is reached. So if the time-out is set to 20 minutes, the files will be deleted 20 minutes after the last access. Same for the cookie. Every time, an page is requested, the cookie-ttl is set to now + 20 minutes.

PHP is a very clean scripting engine, which leaves no garbage on your system!

j a s o n p 0 1 9 at yahoo dot com (13-Jul-2000 09:26)

session_unset() vs. session_destroy():
I would say that the difference is that session_destroy() destroys the session variables, both in the script and where the session data is stored on disk.  session_unset() is like doing a session_unregister() on all registered variables.  They can still be re-registered by calling session_register() whereas after session_destroy, they cannot.