Sulu\Bundle\ContentBundle\Form\Type\PageDocumentType::buildForm PHP Метод

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        parent::buildForm($builder, $options);
        $builder->add('parent', DocumentObjectType::class);
        $builder->addEventListener(FormEvents::POST_SUBMIT, [$this, 'postSubmitDocumentParent']);
    }