Bugfixes: the PHP session handler only fetches the cookie configuration...

Bugfixes: the PHP session handler only fetches the cookie configuration parameters if session_id() returns a non-empty ID. This won't happen if the application initialized a session previously, hijacking the session and causing all kinds of trouble. Instead, we need to detect if there's an active session, save its parameters and close it. After closing it, we can name a new session and set the cookie parameters.