session_cache_expire() returns the current setting of session.cache_expire. The value returned should be read in minutes, defaults to 180. If new_cache_expire is given, the current cache expire is replaced with new_cache_expire.
The cache expire is reset to the default value of 180 stored in session.cache_limiter at request startup time. Thus, you need to call session_cache_expire() for every request (and before session_start() is called).
Note: Setting new_cache_expire is of value only, if session.cache_limiter is set to a value different from nocache.
See also the configuration settings session.cache_expire, session.cache_limiter and session_cache_limiter().