Session dont expire they are destroyed when u call session_destroy() function or the user close the browser ...
Galavantes wrote:certain session ID is still valid. IE: they;ve closed their browser, or lost net connection, or whatever.
as I told u above the sessions dont expire when o connection is lost ...
If u want to see if a user is still logged in to your site, there is a work arround, u set a cookie on the user computer with a date, witch time a user click on your site u update that cookie with the new date, u set an interval on how mutch time a user stay on one page; lets say 15 min; if the date in the cookie is older then 15 min u assume the user has looged out or the user close his browser, it could be a more complex or less complex method, this is only a few words to give u an idea ...