PHP 5.4.36 Released

session_name

(PHP 4, PHP 5)

session_nameGet and/or set the current session name

Description

string session_name ([ string $name ] )

session_name() returns the name of the current session. If name is given, session_name() will update the session name and return the old session name.

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).

Parameters

name

The session name references the name of the session, which is used in cookies and URLs (e.g. PHPSESSID). It should contain only alphanumeric characters; it should be short and descriptive (i.e. for users with enabled cookie warnings). If name is specified, the name of the current session is changed to its value.

Warning

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

Return Values

Returns the name of the current session.

Examples

Example #1 session_name() example

<?php

/* set the session name to WebsiteID */

$previous_name session_name("WebsiteID");

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

See Also

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User Contributed Notes 5 notes

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23
Hongliang Qiang
10 years ago
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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10
relsqui at chiliahedron dot com
5 years ago
Remember, kids--you MUST use session_name() first if you want to use session_set_cookie_params() to, say, change the session timeout. Otherwise it won't work, won't give any error, and nothing in the documentation (that I've seen, anyway) will explain why.

Thanks to brandan of bildungsroman.com who left a note under session_set_cookie_params() explaining this or I'd probably still be throwing my hands up about it.
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7
php at wiz dot cx
6 years ago
if you try to name a php session "example.com" it gets converted to "example_com" and everything breaks.

don't use a period in your session name.
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4
Joseph Dalrymple
3 years ago
For those wondering, this function is expensive!

On a script that was executing in a consistent 0.0025 seconds, just the use of session_name("foo") shot my execution time up to ~0.09s. By simply sacrificing session_name("foo"), I sped my script up by roughly 0.09 seconds.
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2
slave at codegrunt dot com
10 years ago
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
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