session_name

Description

string session_name ( [string name] )

session_name() returns the name of the current session. If name is specified, the name of the current session is changed to its value.

The session name references the session id in cookies and URLs. It should contain only alphanumeric characters; it should be short and descriptive (i.e. for users with enabled cookie warnings). The session name is reset to the default value stored in session.name at request startup time. Thus, you need to call session_name() for every request (and before session_start() or session_register() are called).

警告

Session name can't consist only from digits, at least one letter must be present. Otherwise new session id is generated every time.

例子 1. session_name() examples


<?php

/* set the session name to WebsiteID */

$previous_name = session_name("WebsiteID");

echo "The previous session name was $previous_name<br />";
?>

See also the session.name configuration directive.

add a note User Contributed Notes

Juergen Nantke - info at nantke dot de
10-Aug-2005 11:11


Be carefull not use a dot (.) in the session name.

tjerk dot meesters at gmail dot com
13-Jul-2005 06:32


Another way of preventing a warning being issued, is by using only cookies to propagate a session:



 ini_set('session.use_only_cookies',1);

php at REMOVETHIS dot kennel17 dot co dot uk
27-Jun-2005 10:47


In response to codegrunt slave, you could suppress any warnings from being output by using the @ symbol.



<?php

// This will fail, but no message will be output:

@session_name("(bad name)");

?>



Alternatively, you could use output buffering instead of the @ symbol if you wanted to check whether an error occurred.



<?php

ob_start();

session_name("(bad name)");

$Output = ob_get_contents();

ob_end_clean();

if ($Output != "")

    print("Bad session name!");

?>

slave at codegrunt dot com
23-Dec-2004 06:03


One gotcha I have noticed with session_name is that it will trigger a WARNING level error if the cookie or GET/POST variable value has something other than alphanumeric characters in it.  If your site displays warnings and uses PHP sessions this may be a way to enumerate at least some of your scripts:  



http://example.com/foo.php?session_name_here=(bad)



Warning: session_start(): The session id contains invalid characters, valid characters are only a-z, A-Z and 0-9 in /some/path/foo.php on line 666



I did not see anything in the docs suggesting that one had to sanitize the PHP session ID values before opening the session but that appears to be the case.



Unfortunately session_name() always returns true so you have to actually get to the point of assigning variables values before you know whether you have been passed bad session data (as far as I can see).  After the error has been generated in other words.



Cheers

Hongliang Qiang
28-May-2004 04:48


This may sound no-brainer: the session_name() function will have no essential effect if you set session.auto_start to "true" in php.ini . And the obvious explanation is the session already started thus cannot be altered before the session_name() function--wherever it is in the script--is executed, same reason session_name needs to be called before session_start() as documented.



I know it is really not a big deal. But I had a quite hard time before figuring this out, and hope it might be helpful to someone like me.

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