Symfony2 form to JSON structure

Question

How can the Symfony2 form be transformed to JSON data structure? Looking for proper bundle gave me no results;

Example:

$builder
    ->add('name', 'text')
    ->add('password', 'password')
;

Would result in something like that:

{
    fields: {
        name: {
            type: 'text'
        },
        password: {
            type: 'password'
        }
    }
}

Iterating over each element in form after $form = $this->createForm(new FormType(), new Entity()) was not helpful, could not find some properties that could be defined in form builder.

Answer 1

I assume that you want to get this information in a controller once you have posted the form, in which case you can easily get the underlying entity from the form object, like so:

$entity = $form->getData();

At this point you can either manually pull out the fields you want into an array and json_encode() that, or... implement the JsonSerializable interface in your entity and then directly json_encode() the object itself.

For example:

<?php

namespace FooApp/BarBundle/Entity;

use JsonSerializable;

class Baz implements JsonSerializable
{
    private $name;
    private $password;

    // ...

    function jsonSerialize()
    {
        return [
            'fields' => [
                'name'     => ['type' => $this->name],
                'password' => ['type' => $this->password],
            ],
        ];
    }
}

Then, in your controller:

$entity = $form->getData();
$json = json_encode($entity);

Calling json_encode() will automatically invoke Baz::jsonSerialize() and return the array structure you defined, which in turn is JSON-encoded.

Update 2016-06-23

I happened across this question again by chance - and... I realise that I didn't answer your actual question.

You didn't want to convert the form's underlying entity to JSON - instead you want to represent form structure as data. My apologies for misunderstanding - hopefully I can rectify that with an update.

This is a proof-of-concept that should work for a non-nested form (although it should be straightforward to create a recursive version or something for that case). But, assuming a scenario where you have instantiated a form, comprising of fields name and password, like so:

$form = $this->createForm(FooType::class, $foo);

It should then possible to iterate over the instance and derive a representation of the structure; e.g:

$fields = ['fields' => []];

foreach ($form->all() as $field) {
    $name = $field->getName();
    $type = $field->getConfig()->getType()->getBlockPrefix();
    $fields['fields'][$name] = ['type' => $type];
}

echo json_encode($fields, JSON_PRETTY_PRINT);

Yields:

{
    "fields": {
        "name": {
            "type": "text"
        },
        "password": {
            "type": "password"
        }
    }
}

Hope this helps :)