Be careful if you are updating to PHP 5.6 since the the Sessions's Write behavior changed. It now only writes the session if you changed the data. So this means that if you rely on your session to update an activity time stamp on the server (to control session expiry) you will end up having issues. Here is a quick fix if you are implementing SessionHandlerInterface:
public function close() {
$this->write($this->id, serialize($_SESSION));
return true;
}
Make sure you also use this:
ini_set('session.serialize_handler', 'php_serialize'); // Force standard PHP functions handler for flexibility
More details here:
Request #17860 (Session write short circuit)
https://bugs.php.net/bug.php?id=17860