Symfony: Boolean as [No, Yes] radio Choice list

BoolChoiceType.php

<?php

namespace AppBundle\Form\Type;

use AppBundle\Form\DataTransformer\BoolToIntTransformer;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;

class BoolChoiceType extends AbstractType
{

    /**
     * @inheritdoc
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $nullable = $options['placeholder'] !== null;
        $builder->addModelTransformer(new BoolToIntTransformer($nullable));
    }

    /**
     * @inheritdoc
     */
    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            'expanded' => true,
            'no_label' => 'No',
            'yes_label' => 'Yes',
        ]);

        $resolver->setNormalizer('choices', function ($options, $choices) {
            $choices[0] = $options['no_label'];
            $choices[1] = $options['yes_label'];
            return $choices;
        });
    }

    /**
     * @inheritdoc
     */
    public function getParent()
    {
        return 'choice';
    }

    /**
     * @inheritdoc
     */
    public function getName()
    {
        return 'bool_choice';
    }
}

BoolToIntTransformer.php

<?php

namespace AppBundle\Form\DataTransformer;

use Symfony\Component\Form\DataTransformerInterface;
use Symfony\Component\Form\Exception\TransformationFailedException;

class BoolToIntTransformer implements DataTransformerInterface
{
    /**
     * @var bool
     */
    private $nullable;
    /**
     * @var mixed
     */
    private $nullValue;

    public function __construct($nullable = true, $nullValue = '')
    {
        $this->nullValue = $nullValue;
        $this->nullable = $nullable;
    }

    /**
     * @inheritdoc
     */
    public function transform($value)
    {
        var_dump(['transform' => $value]);
        if ($this->nullable && $value === null) {
            return $this->nullValue;
        }
        return (int) $value;
    }

    /**
     * @inheritdoc
     */
    public function reverseTransform($value)
    {
        var_dump(['reverseTransform' => $value]);
        if ($this->nullable && $value === $this->nullValue) {
            return null;
        }
        return (bool) $value;
    }
}