Sessions again....

Hello, I am trying to understand how sessions work. I have this code. My understanding is after 1 sec of script completion, (may be little after that), the session should destroy. I understand that it is huge overhead for server, not planning to do this but want to understand how it really works. This server uses cookie to store session. Setings in php.ini file are defaut (1440 and probility is 1) ini_set('session.auto_start', '0'); session_id('SSP'); session_cache_limiter("nocache"); ini_set('session.cookie_lifetime', '0'); ini_set('session.gc_probability', '100'); ini_set('session.gc_divisor', '100'); ini_set('session.gc_maxlifetime', '1'); session_start(); if(!session_is_registered('count')) session_register('count'); echo ++$_SESSION['count']; Any help will be appriciated! Thanks SP