public static function create($environment, $debug)
 {
     if (self::$_instance) {
         return self::$_instance;
     }
     $instance = new self();
     $instance->environment = $environment;
     $instance->debug = (bool) $debug;
     $instance->registerModuleDirectory(realpath(__DIR__ . '/../../../'));
     self::$_instance = $instance;
     return $instance;
 }