Doctrine - ManyToMany Self Referencing Association + nested toArray() on child elements - symfony

Question

I'm trying to perform a ManyToMany self referencing association in my Symfony 2.1 project by following the Doctrine docs: http://docs.doctrine-project.org/en/latest/reference/association-mapping.html#many-to-many-self-referencing
My use-case is that I'm working on a CMS and I'm adding the ability to have related items of content. For example: I could have a sidebar on a website which would say that this piece of content X is related to Y and Z. Similarly on pages where content Y appears it says that it is related to content item X.
In my tests using this to add a new relation between content items fails because it reaches PHP's maximum nesting level of 100 because it is running toArray() on the current content item and then again on the related content item and so on and so on.
I've seen many similar questions on SO about Many-to-Many Self referential Doctrine associations but none with enough complete code to be able to see how others have managed this. Can anybody help?
My Content entity:
/**
* #ORM\MappedSuperclass
* #ORM\Table(name="content")
* #ORM\Entity(repositoryClass="CMS\Bundle\Common\ContentBundle\Entity\ContentRepository")
* #ORM\InheritanceType("JOINED")
*/
abstract class content implements ContentInterface
{
/**
* #var int $id
*
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
/**
* #var string $title
*
* #ORM\Column(name="title", type="string", length=255)
* #Assert\NotBlank()
*/
private $title;
// Other class properties
/**
* #var array
*
* #ORM\ManyToMany(targetEntity="Content", cascade={"persist"})
* #ORM\JoinTable(name="content_relation",
* joinColumns={#ORM\JoinColumn(name="relation_id", referencedColumnName="id")},
* inverseJoinColumns={
* #ORM\JoinColumn(name="related_content_id", referencedColumnName="id")
* })
**/
private $related;
public function __construct()
{
$this->related = new ArrayCollection();
}
// Other getters & setters for class properties
/**
* #return array
*/
public function getRelated()
{
return $this->related;
}
/**
* #param Content $relation
*/
public function addRelation(Content $relation)
{
$this->related->add($relation);
$this->related->add($this);
}
/**
* #return array
*/
public function toArray()
{
$related = array();
foreach($this->getRelated() as $relatedItem) {
$related[] = $relatedItem->toArray();
}
return array(
'type' => static::getType(),
'id' => $this->id,
'title' => $this->title,
....
'related' => $related
);
}
In my RelationsController for managing the related content data I use it like this:
/**
* Creates a new relation to a content item
*
* #Route("{_locale}/content/{id}/related", name="relation_add")
* #Method("POST")
*/
public function addAction(Request $request, $id)
{
// Validation and error checking
// $entity is loaded by the repository manager doing a find on the passed $id
$entity->addRelation($relation);
$em = $this->getEntityManager();
$em->persist($entity);
$em->persist($relation);
$em->flush();
$response = $relation->toArray();
return new JsonResponse($response, 201);
}

Answer 1

The fix for this was to use the JMSSerializerBundle to encode the entity to JSON instead of using a toArray method and change the addRelation function to:
/**
* #param Content $relation
*/
public function addRelation(Content $relation)
{
$this->related[] = $relation;
if (! $relation->getRelated()->contains($this)) {
$relation->addRelation($this);
}
}