static function getInstance() { if (empty(self::$instance)) { switch (_RELEASE) { case "fermi": if (!file_exists(_ABSPATH . '/lib/DevicesFermi.php')) { die("Fermi Devices class does not exist"); } require_once _ABSPATH . '/lib/DevicesFermi.php'; self::$instance = new DevicesFermi(); break; case "general": default: if (!file_exists(_ABSPATH . '/lib/DevicesGeneral.php')) { die("General Devices class does not exist"); } require_once _ABSPATH . '/lib/DevicesGeneral.php'; self::$instance = new DevicesGeneral(); break; } } return self::$instance; }