Form
====

The *FormServiceProvider* provides a service for building forms in
your application with the Symfony Form component.

Parameters
----------

* **form.secret**: This secret value is used for generating and validating the
  CSRF token for a specific page. It is very important for you to set this
  value to a static randomly generated value, to prevent hijacking of your
  forms. Defaults to ``md5(__DIR__)``.

Services
--------

* **form.factory**: An instance of `FormFactory
  <http://api.symfony.com/master/Symfony/Component/Form/FormFactory.html>`_,
  that is used to build a form.

* **form.csrf_provider**: An instance of an implementation of
  `CsrfProviderInterface
  <http://api.symfony.com/2.3/Symfony/Component/Form/Extension/Csrf/CsrfProvider/CsrfProviderInterface.html>`_ for Symfony 2.3 or
  `CsrfTokenManagerInterface <http://api.symfony.com/2.7/Symfony/Component/Security/Csrf/CsrfTokenManagerInterface.html>`_ for Symfony 2.4+.

Registering
-----------

.. code-block:: php

    use Silex\Provider\FormServiceProvider;

    $app->register(new FormServiceProvider());

.. note::

    If you don't want to create your own form layout, it's fine: a default one
    will be used. But you will have to register the :doc:`translation provider
    <translation>` as the default form layout requires it.

    If you want to use validation with forms, do not forget to register the
    :doc:`Validator provider <validator>`.

.. note::

    The Symfony Form Component and all its dependencies (optional or not) comes
    with the "fat" Silex archive but not with the regular one. If you are using
    Composer, add it as a dependency:

    .. code-block:: bash

        composer require symfony/form

    If you are going to use the validation extension with forms, you must also
    add a dependency to the ``symfony/config`` and ``symfony/translation``
    components:

    .. code-block:: bash

        composer require symfony/validator symfony/config symfony/translation
        
    The Symfony Security CSRF component is used to protect forms against CSRF
    attacks (as of Symfony 2.4+):

    .. code-block:: bash
    
        composer require symfony/security-csrf

    If you want to use forms in your Twig templates, you can also install the
    Symfony Twig Bridge. Make sure to install, if you didn't do that already,
    the Translation component in order for the bridge to work:

    .. code-block:: bash

        composer require symfony/twig-bridge symfony/config symfony/translation

Usage
-----

The FormServiceProvider provides a ``form.factory`` service. Here is a usage
example::

    $app->match('/form', function (Request $request) use ($app) {
        // some default data for when the form is displayed the first time
        $data = array(
            'name' => 'Your name',
            'email' => 'Your email',
        );

        $form = $app['form.factory']->createBuilder('form', $data)
            ->add('name')
            ->add('email')
            ->add('billing_plan', 'choice', array(
                'choices' => array(1 => 'free', 2 => 'small_business', 3 => 'corporate'),
                'expanded' => true,
            ))
            ->getForm();

        $form->handleRequest($request);

        if ($form->isValid()) {
            $data = $form->getData();

            // do something with the data

            // redirect somewhere
            return $app->redirect('...');
        }

        // display the form
        return $app['twig']->render('index.twig', array('form' => $form->createView()));
    });

And here is the ``index.twig`` form template (requires ``symfony/twig-bridge``):

.. code-block:: jinja

    <form action="#" method="post">
        {{ form_widget(form) }}

        <input type="submit" name="submit" />
    </form>

If you are using the validator provider, you can also add validation to your
form by adding constraints on the fields::

    use Symfony\Component\Validator\Constraints as Assert;

    $app->register(new Silex\Provider\ValidatorServiceProvider());
    $app->register(new Silex\Provider\TranslationServiceProvider(), array(
        'translator.domains' => array(),
    ));

    $form = $app['form.factory']->createBuilder('form')
        ->add('name', 'text', array(
            'constraints' => array(new Assert\NotBlank(), new Assert\Length(array('min' => 5)))
        ))
        ->add('email', 'text', array(
            'constraints' => new Assert\Email()
        ))
        ->add('billing_plan', 'choice', array(
            'choices' => array(1 => 'free', 2 => 'small_business', 3 => 'corporate'),
            'expanded' => true,
            'constraints' => new Assert\Choice(array(1, 2, 3)),
        ))
        ->getForm();

You can register form types by extending ``form.types``::

    $app['form.types'] = $app->share($app->extend('form.types', function ($types) use ($app) {
        $types[] = new YourFormType();

        return $types;
    }));

You can register form extensions by extending ``form.extensions``::

    $app['form.extensions'] = $app->share($app->extend('form.extensions', function ($extensions) use ($app) {
        $extensions[] = new YourTopFormExtension();

        return $extensions;
    }));


You can register form type extensions by extending ``form.type.extensions``::

    $app['form.type.extensions'] = $app->share($app->extend('form.type.extensions', function ($extensions) use ($app) {
        $extensions[] = new YourFormTypeExtension();

        return $extensions;
    }));

You can register form type guessers by extending ``form.type.guessers``::

    $app['form.type.guessers'] = $app->share($app->extend('form.type.guessers', function ($guessers) use ($app) {
        $guessers[] = new YourFormTypeGuesser();

        return $guessers;
    }));

Traits
------

``Silex\Application\FormTrait`` adds the following shortcuts:

* **form**: Creates a FormBuilder instance.

.. code-block:: php

    $app->form($data);

For more information, consult the `Symfony Forms documentation
<http://symfony.com/doc/2.3/book/forms.html>`_.
