nineskeletor/src/Form/BlogType.php

<?php

namespace App\Form;

use Symfony\Bridge\Doctrine\Form\Type\EntityType;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\Extension\Core\Type\SubmitType;
use Symfony\Component\Form\Extension\Core\Type\TextType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;

class BlogType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('submit', SubmitType::class, [
                'label' => 'Valider',
                'attr' => ['class' => 'btn btn-success'],
            ])

            ->add('name', TextType::class, [
                'label' => 'Titre',
            ])

            ->add('blogtype', EntityType::class, [
                'label' => 'Type',
                'class' => 'App\Entity\Blogtype',
                'choice_label' => 'name',
            ]);
    }

    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            'data_class' => 'App\Entity\Blog',
            'mode' => 'string',
            'blogtype' => 'App\Entity\Blogtype',
        ]);
    }
}