if(session_id() == '') {
session_start();
}
if (isset($_SESSION['LAST_ACTIVITY']) && (time() - $_SESSION['LAST_ACTIVITY'] > 1400)) {
// last request was more than 30 minutes ago
session_unset(); // unset $_SESSION variable for the run-time
session_destroy(); // destroy session data in storage
session_start();
}
$_SESSION['LAST_ACTIVITY'] = time(); // update last activity time stamp