public static function getInstance() { if (is_null(self::$instance)) { self::$instance = new self(); } return self::$instance; }
public static function getInstance($sub_ = null) { if (is_null(self::$instance)) { self::$instance = new self(); } if (!is_null($sub_)) { if (!array_key_exists($sub_, self::$instance->instance_type)) { return null; } return self::$instance->instance_type[$sub_]; } return self::$instance; }