create a Custom Form Field Type with json_array

[13]

Hi,

How can I create a Custom Form Field Type with json_array.
I just want to save a couple of information.

Ex :

["key":"78915547","secret_key":"75845", "public_key":"78945"...]

Admin Class:

protected function configureFormFields(FormMapper $formMapper) {
               $formMapper ->add('extra_params', 'extra_param_collection', array(
                    'allow_add' => true,
                ))...

Custom Form Type :

<?php

namespace Application\Sonata\UserBundle\Form\Type;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Symfony\Component\Form\FormView;
use Symfony\Component\Form\FormInterface;
use Symfony\Component\Form\FormBuilderInterface;

class ExtraParamCollectionType extends AbstractType {

 public function getParent() {
 return 'collection';
 }

 public function getName() {
 return 'extra_param_collection';
 }
}

Service :
 extra_param_collection:
 class: Application\Sonata\UserBundle\Form\Type\ExtraParamCollectionType
 tags:
 - { name: form.type }

Entity:
/**
 * @var string
 *
 * @ORM\Column(type="json_array", length=512, nullable=true)
 */
 private $extra_params;


How i can display in my form many fields and how to save it in this format? 

Thank you in advance

[13]

Found :

https://github.com/Burgov/KeyValueFormBundle

Exactly what I need :)