gistfile1.php

<?php

use Symfony\Component\Form\Forms;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Form\FormEvent;
use Symfony\Component\Form\FormEvents;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

class ApplicationFormType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('title', 'text', array(
            'label'       => 'Application title',
        ));
        $builder->add('description', 'text', array(
            'label'       => 'Application description',
        ));

        $builder->setData(array(
            'title' => 'A default title',
            'description' => 'A default description',
        ));
        
        $builder->addEventListener(FormEvents::PRE_SUBMIT, function (FormEvent $event) use (&$defaultData) {
            $defaultData = $event->getForm()->getData();
            var_dump($defaultData);
        }, 255);
    }

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

$factory = Forms::createFormFactoryBuilder()->getFormFactory();
$form = $factory->create(new ApplicationFormType());
$form->submit(array());

// expecting array('title' => 'A defaut title', 'description' => 'A defaut description') but got null
var_dump($form->getData());