Other functions

bool session_is_registered ( string $name )
Finds out whether a global variable is registered in a session.

bool isset($_SESSION[$name]) may also be used.

void session_unset ( void )
The session_unset() function frees all session variables currently registered.
No value is returned.

bool session_unregister ( string $name )
session_unregister() unregisters the global variable named name from the current session.
string session_save_path ([ string $path ] )
session_save_path() returns the path of the current directory used to save session data.

bool session_destroy ( void )
session_destroy() destroys all of the data associated with the current session. It does not unset any of the global variables associated with the session, or unset the session cookie.
Returns TRUE on success or FALSE on failure.