Get and/or set the current session name
(PHP 4, PHP 5)
Example 2225. session_name() example
Related Examples ( Source code ) » session_name
Code Examples / Notes » session_name
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.
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:
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.
In response to codegrunt slave, you could suppress any warnings from being output by using the @ symbol.
// This will fail, but no message will be output:
Alternatively, you could use output buffering instead of the @ symbol if you wanted to check whether an error occurred.
$Output = ob_get_contents();
if ($Output != "")
print("Bad session name!");