Константин Грачев

$form = $this->createCreateForm($entity);
$form->handleRequest($request);

if ($form->isValid()) {
    $em->persist($entity);
    $em->flush();

    if ($request->isXmlHttpRequest()) {
        return new JsonResponse([
            'id' => $entity->getId(),
        ]);
    }

    return $this->redirectToRoute('route');
}