(PHP 5 >= 5.4.0, PHP 7, PHP 8)
SessionHandlerInterface::open — Initialisiert eine Session
Initialisiert eine bestehende Session neu oder erstellt eine neue. Wird aufgerufen, wenn eine Session startet oder wenn session_start() aufgerufen wird.
pathDer Pfad, unter dem die Session gespeichert/abgerufen werden soll
nameDer Name der Session
Der Rückgabewert (normalerweise true bei Erfolg und false bei Misserfolg). Es ist zu beachten, dass dieser Wert intern PHP zur Verarbeitung zurückgegeben wird.
The suggestion that you should free the lock as soon as possible is WRONG (and for some reason, I can't downvote it right now).
Releasing the lock before the write() call is as effective as not using locks at all. The whole point is that a concurrent read() HAS to be blocked until the session is closed, otherwise you'll have race conditions.
If you care about the performance aspect, you should take care to call session_write_close() as soon as possible instead.Note that once $sessionName has been used to provide a value for $sessionId from the cookie data it is totally redundant as all further reading and writing of the session data is controlled by $sessionId.
If, for any reason, it becomes necessary to identify the value for $sessionName which is associated with the current $sessionId then you should use the value that was passed on the open() method. Attempting to use a value from an alternative source could have unexpected side effects.