serializer = $serializer; $this->callback = $callback; } public function extend(Container $container) { $container->make('events')->listen('Flarum\Api\Events\SerializeAttributes', function ($event) { if ($event->serializer instanceof $this->serializer) { call_user_func_array($this->callback, [&$event->attributes, $event->model, $event->serializer]); } }); } }