Serializing FormView data in JSON - php

Question

I am trying to change the approach of rendering templates. I was using a server-side template engine. Now that I need to return only JSON from backend instead of HTML, I need to move my templating to front-end.
The problem for me as a newbie, is when the template contains a form. In other words, when the final JSON should also contain a csrf token. Please to take the example of CRUD application for books (one entity Book(id_book, name)). The template for Reading a record shows the book name and allow deletion of a book.
In Symfony2 controller, I use createFormBuilder() method that creates the delete form object, to which I apply createView()method. The object returned by the latter is used by form_widget()in the template engine (Twig). At the end:
<div id="bookName">{{book.name}}</div>
<div id="bookDelete">
<form action="{{ path('book_delete', { 'id': book.id }) }}" method="post">
<input type="hidden" name="_method" value="DELETE" />
{{ form_widget(delete_form) }}
<button type="submit"></button>
</form>
</div>
Which will return:
<div id="bookName">Symfony2 In Depth</div>
<div id="bookDelete">
<form action="/web/app_dev.php/deletes" method="post">
<input type="hidden" name="_method" value="DELETE">
<div id="form">
<input type="hidden" id="form_id" name="form[id]" value="15">
<input type="hidden" id="form__token" name="form[_token]" value="dd6573ae916ae30f78ba35a8c67e5d42a2764c1c">
</div>
<button type="submit"></button>
</form>
What I imagine when moving template rendering to front-end is a final JSON from server looking like:
{
'id':15,
'name': 'Symfony2 in Depth',
'csrf_token' : 'dd6573ae916ae30f78ba35a8c67e5d42a2764c1c'
}
Question is how to implement the same Symfony2 internal mechanism to render csrf token for DELETE form, as part of the final JSON to read a book entity? Is it acceptable to get rid of {{ form_widget(delete_form) }} and all its long objects, and only serialize csrf token with book name? What does this will affect? I feel it is good for performance but how?
Your usual guidance is much appreciated.

Answer 1

You can create you twig file something like:
{
'id': '{{ form.id.vars.value }}'
'name': '{{ form.name.vars.value }}'
'csrf_token': '{{ form._token.vars.value }}'
}
Anyway I dont recommend you use csrf token when you are using API, it is better if you disabled. If you want to disable for all application in the config.yml:
framework:
csrf_protection:
enabled: false
Or just for one form in the Type form add:
public function configureOptions(OptionsResolver $resolver)
{
$resolver->setDefaults(array(
'csrf_protection' => false,
));
}