Symfony2: Persisting embedded collection within self-referencing embedded collection - symfony

Question

Overview
I have two entities;
Element
ElementAnswer
Element has a self-referencing relation and ElementAnswer has a One-To-Many relation with Element (One Element can have many ElementAnswers).
I'm using Symfony2 with embedded collection and it's is working (together with javasript). I can add multiple 'child' elements to the 'parent' element. Also i can add multiple answers to the child element. But.. When i add a child element and add answers to the child element only the child element gets persisted. The answers (which is an embedded collection to the child elements) don't get persisted. AND when i edit the whole collection the answers are persisted.
To be more precise i made some screenshots AND i debugged the post data. Which is exactly the same.
ElementType:
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('name')
->add('question')
//->add('answers')
->add('answers', 'collection', array(
'entry_type' => new AnswerType(),
'allow_add' => true,
'by_reference' => false,
'allow_delete' => true,
'empty_data' => null,
))
->add('conditions', 'collection', array(
'entry_type' => new ConditionalType(),
'allow_add' => true,
'by_reference' => false,
'allow_delete' => true,
'empty_data' => null,
))
//->add('children', )
->add('children', 'collection', array(
'entry_type' => new ElementChildType(),
'allow_add' => true,
'by_reference' => false,
'allow_delete' => true,
'empty_data' => null,
))
;
}
ElementChildType:
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('name')
->add('answers', 'collection', array(
'entry_type' => new AnswerType(),
'allow_add' => true,
'by_reference' => false,
'allow_delete' => true,
'empty_data' => null,
'block_name' => 'child_element_answer',
'prototype_name' => '__child_element_answer__',
))
;
}
This is how the form looks like before i submit it:
(Child element 1 and 2 are already persisted. Child element 3 is a newly added entity in the form
This is the post data:
element[name]:parent-element-name
element[question]: blabla
element[children][0][name]:child element 1
element[children][0][answers][0][name]:child answer 1-1
element[children][1][name]:child element 2
element[children][1][answers][0][name]:child answer 2-1
element[children][2][name]:child element 3
element[children][2][answers][0][name]:child answer 3-1
element[_token]:xxxxxxxxxxxxxxxxxxxxxxxxxxxx
This is how the form looks like after submit:
(As you can see: there is no child answer in child element 3)
And when i add a child answer now (after submitting) the child answer DOES get persisted. The same controller is being called and the same entities, so i am stuck. Please help. Thank you!
EDIT:
I finally edited my controller the following way. Probably not the best practice, but it's working so i thought i should let you know:
/**
* Displays a form to edit an existing Element entity.
*
* #Route("/{id}/edit", name="element_edit")
* #Method({"GET", "POST"})
*/
public function editAction(Request $request, Element $element, $firstPost = NULL)
{
$em = $this->getDoctrine()->getManager();
$deleteForm = $this->createDeleteForm($element);
$editForm = $this->createForm('AppBundle\Form\ElementType', $element);
$editForm->handleRequest($request);
$breadcrumbs = array();
$breadcrumbs[] = array("name" => "Dashboard", "url" => $this->get("router")->generate("dashboard"));
$breadcrumbs[] = array("name" => "Elementen lijst", "url" => $this->get("router")->generate("element_index"));
$breadcrumbs[] = array("name" => "Element bewerken");
if ($editForm->isSubmitted() && $editForm->isValid()) {
$originalChildren = new ArrayCollection();
$postChildren = new ArrayCollection();
$newChildren = new ArrayCollection();
foreach ($element->getChildren() as $child) {
$originalChildAnswers = new ArrayCollection();
$originalChildren->add($child);
foreach ($child->getAnswers() as $childAnswer) {
$originalChildAnswers->add($childAnswer);
}
}
if (isset($request->request->get('element')['children'])) {
foreach ($request->request->get('element')['children'] as $postChild) {
$postChildren->add($postChild);
}
}
$newElements = [];
$i = 0;
foreach ($originalChildren as $child) {
if (null != $child->getId() && $element->getChildren()->contains($child)) {
$i++;
} else {
$newElements[] = $i;
$i++;
}
}
foreach ($newElements as $newElement) {
$newChildren->set($newElement, $postChildren[$newElement]);
}
foreach ($newChildren as $key => $newchild) {
foreach ($newchild['answers'] as $newChildAnswer) {
$childAnswerKey = $element->getChildren()->getKeys()[$key];
$answerEntity = new Answer();
$answerEntity->setName($newChildAnswer['name']);
$element->getChildren()[$childAnswerKey]->addAnswer($answerEntity);
}
}
$em->persist($element);
$em->flush();
return $this->redirectToRoute('element_edit', array('id' => $element->getId()));
}
return $this->render('element/edit.html.twig', array(
'breadcrumbs' => $breadcrumbs,
'element' => $element,
'edit_form' => $editForm->createView(),
'delete_form' => $deleteForm->createView(),
));
}