DefaultController.php from https://www.symfony.fi/entry/sharing-state-in-a-symfony-hybrid-app-with-twig-react-etc

DefaultController.php

public function apiApartmentsAction(Request $request)
{

    $appState = new AppState();

    $em = $this->get('doctrine.orm.default_entity_manager');
    $apartments = $em->getRepository('AppBundle:Apartment')->getRandom(10);

    $appState->setApartments($apartments);
    $response = new JsonResponse();

    $response->setContent($appState->jsonSerialize());

    return $response;

}