public static function init($guid = null)
{
if (!self::$instance instanceof Session) {
session_start();
self::$instance = new Session();
if ($guid != null && $guid != '') {
self::$guid = $guid;
} else {
self::$guid = "no_guid_set";
trigger_error('No GUID set for Session class', E_USER_NOTICE);
}
}
}