How to show null value in JSON in FOS Rest Bundle with JMS Serializer?

You can set the following option in the config since recently:

fos_rest:    serializer:        serialize_null: true

Try this

in your controller

    $entity = $this->getEntity($id);    $context = new SerializationContext();    $context->setSerializeNull(true);    $serializer = $this->get('jms_serializer');    $response = new Response($serializer->serialize($entity, 'json', $context));    $response->headers->set('Content-Type', 'application/json');    return $response;

But the interaction with the fosrestbundle about configs is not known to me.

The easiest way to make this feature works like a charm

Add the following extra configuration to your fos_rest config option:

fos_rest:    serializer:        serialize_null: true