static function get_instance() { if (!isset(self::$obj_instance)) { self::$obj_instance = new self(); session_set_save_handler(array(self::$obj_instance, "open"), array(self::$obj_instance, "close"), array(self::$obj_instance, "read"), array(self::$obj_instance, "write"), array(self::$obj_instance, "destroy"), array(self::$obj_instance, "gc")); session_start(); } return self::$obj_instance; }