Symfony4 returning serialized json repsonse - doctrine-orm

Question

I'm looking at a new Symfony5 project , where I'm trying to return a JSON response of some data.
I have a Project and a ProjectItem
I have the following:
// Project.php
/**
* #ORM\OneToMany(targetEntity="App\Entity\ProjectItem", mappedBy="project")
*/
private $projectItems;
// ProjectItem.php
/**
* #ORM\ManyToOne(targetEntity="App\Entity\Project", inversedBy="projectItems")
*/
private $project;
I have one Project, that can have many ProjectItems
I then have a controller that I'm trying to return a json response:
public function index()
{
$itemsList = $this->getDoctrine()
->getRepository(Project::class)
->findAll();
$items = $this->get('serializer')->serialize($itemsList, 'json');
return new Response($items, 200);
}
This is currently returning an error:
A circular reference has been detected when serializing the object of class "App\Entity\Project" (configured limit: 1)
Am I using the serializer correctly or are my models incorrectly configured?

Answer 1

Simply use json_encode:
public function index()
{
$itemsList = $this->getDoctrine()
->getRepository(Project::class)
->findAll();
return new Response(
json_encode($itemsList),
200
);
}
or use JsonResponse class:
return new JsonResponse($itemsList);

Answer 2

You have a circular reference with your relations. Im guessing ProjectItem has a field project that is referencing Project which causes a loop for the serializer. You can ignore said attribute to prevent this from happening. Checkout the ignored attributes section of the serializer documentation.
Another option would be to use Serialization Groups. Every property would get a Group annotation like for example #Groups("group1") excluding that reference property back to Project.
You would then tell the serializer to serialize that group:
$json = $serializer->serialize(
$itemList,
'json', ['groups' => 'group1']
);
You may also checkout JMS Serializer which adds #Exclude and #Include annotations to make this step a bit easier.