<?php

namespace Customize\Form\Extension\Shopping;

use Eccube\Entity\Order;
use Eccube\Form\Type\Shopping\OrderType;
use Symfony\Bridge\Doctrine\Form\Type\EntityType;
use Symfony\Component\Form\AbstractTypeExtension;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\Extension\Core\Type\TextareaType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Symfony\Component\Validator\Constraints as Assert;
use Customize\Form\Type\Master\ExampleType;

class OrderTypeExtension extends AbstractTypeExtension
{
    /**
     * {@inheritdoc}
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        //☆追加した部分
        if ($options['skip_add_form']) {
            return;
        }
        //追加した部分 END

        $builder->add('example_id', ExampleType::class, [
            'label' => 'テストです',
            'required' => true,
            'expanded' => true,
            'multiple' => false,
            'constraints' => [
                new Assert\NotBlank(),
            ],
        ]);
    }

    /**
     * {@inheritdoc}
     */
    public function getExtendedType()
    {
        return OrderType::class;
    }
}

if ($options['skip_add_form']) {
    return;
}

// フォームの生成.
        $form = $this->createForm(OrderType::class, $Order, [
            // 確認画面から注文処理へ遷移する場合は, Orderエンティティで値を引き回すためフォーム項目の定義をスキップする.
            'skip_add_form' => true,
        ]);
        $form->handleRequest($request);
        var_dump($Order->getExampleId());exit; //☆この部分で取得した値がNullになっている。
        if ($form->isSubmitted() && $form->isValid()) {
            log_info('[注文処理] 注文処理を開始します.', [$Order->getId()]);

            try {
                /*
                 * 集計処理
                 */
                log_info('[注文処理] 集計処理を開始します.', [$Order->getId()]);
                $response = $this->executePurchaseFlow($Order);
                $this->entityManager->flush();

<?php

namespace Customize\Repository\Master;

use Customize\Entity\Master\Example;
use Symfony\Bridge\Doctrine\RegistryInterface;
use Eccube\Repository\AbstractRepository;

class ExampleRepository extends AbstractRepository
{
    public function __construct(RegistryInterface $registry)
    {
        parent::__construct($registry, Example::class);
    }
}

<?php

namespace Customize\Entity\Master;

use Doctrine\ORM\Mapping as ORM;

/**
 * Example
 *
 * @ORM\Table(name="mtb_example")
 * @ORM\InheritanceType("SINGLE_TABLE")
 * @ORM\DiscriminatorColumn(name="discriminator_type", type="string", length=255)
 * @ORM\HasLifecycleCallbacks()
 * @ORM\Entity(repositoryClass="Customize\Repository\Master\ExampleRepository")
 * @ORM\Cache(usage="NONSTRICT_READ_WRITE")
 */
class Example extends \Eccube\Entity\Master\AbstractMasterEntity
{
}
}

<?php

namespace Customize\Form\Type\Master;

use Eccube\Form\Type\MasterType;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;

class ExampleType extends AbstractType
{
    /**
     * {@inheritdoc}
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $options['example_options']['required'] = $options['required'];
    }

    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            'class' => 'Customize\Entity\Master\Example',
            'expanded' => true,
            'placeholder' => false,
        ]);
    }

    public function getParent()
    {
        return MasterType::class;
    }

    public function getBlockPrefix()
    {
        return 'example';
    }
}

<?php

namespace Customize\Form\Extension\Shopping;

use Eccube\Entity\Order;
use Eccube\Form\Type\Shopping\OrderType;
use Symfony\Bridge\Doctrine\Form\Type\EntityType;
use Symfony\Component\Form\AbstractTypeExtension;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\Extension\Core\Type\TextareaType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Symfony\Component\Validator\Constraints as Assert;
use Customize\Form\Type\Master\ExampleType;

class OrderTypeExtension extends AbstractTypeExtension
{
    /**
     * {@inheritdoc}
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('example_id', ExampleType::class, [
            'label' => 'テストです',
            'required' => true,
            'expanded' => true,
            'multiple' => false,
            'constraints' => [
                new Assert\NotBlank(),
            ],
        ]);
    }

    /**
     * {@inheritdoc}
     */
    public function getExtendedType()
    {
        return OrderType::class;
    }
}

<?php

namespace Customize\Entity;

use Doctrine\ORM\Mapping as ORM;
use Eccube\Annotation as Eccube;
use Symfony\Component\Validator\Constraints as Assert;

/**
 * @Eccube\EntityExtension("Eccube\Entity\Order")
 */
trait OrderTrait
{
    /**
     * @var \Customize\Entity\Master\Example
     * @ORM\ManyToOne(targetEntity="Customize\Entity\Master\Example")
     * @ORM\JoinColumns({
     *   @ORM\JoinColumn(name="example_id", referencedColumnName="id", nullable=true)
     * })
     */
    private $Example;

    /**
     * @param \Customize\Entity\Master\Example|null $example_id
     * @return Order
     */
    public function setExampleId(\Customize\Entity\Master\Example $example_id = null)
    {
        $this->Example = $example_id;
        return $this;
    }

    /**
     * @return \Customize\Entity\Master\Example|null
     */
    public function getExampleId()
    {
        return $this->Example;
    }
}