php expire session
//Ending a php session after 30 minutes of inactivity
$minutesBeforeSessionExpire=30;
if (isset($_SESSION['LAST_ACTIVITY']) && (time() - $_SESSION['LAST_ACTIVITY'] > ($minutesBeforeSessionExpire*60))) {
session_unset(); // unset $_SESSION
session_destroy(); // destroy session data
}
$_SESSION['LAST_ACTIVITY'] = time(); // update last activity