My First a Usecase.php

UserRegisterUsecase.php

<?php

namespace Demo\AdminBundle\Usecase;

use JMS\DiExtraBundle\Annotation\Inject;
use JMS\DiExtraBundle\Annotation\InjectParams;
use JMS\DiExtraBundle\Annotation\Service;
use Doctrine\ORM\EntityManager;
use FOS\UserBundle\Doctrine\UserManager;
use Demo\UserBundle\Usecase\UsecaseInterface;
use Demo\UserBundle\Entity\User;

/**
 * @Service("demo.usecase.user_register")
 */
class UserRegisterUsecase implements UsecaseInterface
{
    /**
     * @var EntityManager
     */
    private $entityManager;

    /**
     * @var UserManager
     */
    private $userManager;

    /**
     * @InjectParams({
     *     "entityManager" = @Inject("doctrine.orm.entity_manager"),
     *     "userManager"   = @Inject("fos_user.user_manager")
     * })
     */
    public function __construct(EntityManager $entityManager, UserManager $userManager)
    {
        $this->entityManager = $entityManager;
        $this->userManager   = $userManager;
    }

    /**
     * @param $user
     * @return mixed
     */
    public function run(User $user)
    {
        $this->entityManager->persist($user);
        $this->entityManager->flush();

        return $user;
    }
}