Session Garbage Collection Observation:
It appears that session file garbage collection occurs AFTER the current session is loaded.
This means that:
even if session.gc_maxlifetime = 1 second,
if someone starts a session A and no one starts a session for an hour, that person can reconnect to session A and all of their previous session values will be available (That is, session A will not be cleaned up even though it is older than gc_maxlifetime).