How often does a PHP session ID change per user? -

How often does a PHP session ID change per user? -

just basic question, if open session when user visits main page , store session id. when user homecoming day/time , id different?

this depends on how php configured. these settings command how php session id "erased" garbage collector:

http://php.net/manual/en/session.configuration.php#ini.session.gc-maxlifetime

session.gc_maxlifetime specifies number of seconds after info seen 'garbage' , potentially cleaned up. garbage collection may occur during session start (depending on session.gc_probability , session.gc_divisor).

http://php.net/manual/en/session.configuration.php#ini.session.gc-divisor

session.gc_divisor coupled session.gc_probability defines probability gc (garbage collection) process started on every session initialization. probability calculated using gc_probability/gc_divisor, e.g. 1/100 means there 1% chance gc process starts on each request. session.gc_divisor defaults 100.

http://php.net/manual/en/session.configuration.php#ini.session.gc-probability

session.gc_probability in conjunction session.gc_divisor used manage probability gc (garbage collection) routine started. defaults 1. see session.gc_divisor details.

as far know default php session.gc_maxlifetime 1440 seconds (24 minutes). more visits have in site "accurate" these statistics since algorithm run more often.

a tricky edge case: if start session , never other visit site, garbage collector algorithm never run, hence session never expire! if can understand this, think have understood answer.

php session