Entity.php

<?php
// src/Acme/SubscriptionBundle/Entity/Transaction.php 

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

class Transaction
{
    /**
     * @Assert\Luhn(message = "Please check your credit card number.")
     * @ORM\Column(type="string", length=255)
     */
    protected $cardNumber;

    /**
     * @ORM\OneToMany(targetEntity="User", mappedBy="transactions")
     * @Assert\NotBlank()
     */
    protected $user;

    /**
     * @ORM\OneToMany(targetEntity="UserAddress")
     * @Assert\NotBlank()
     */
    protected $address;

    /**
     * @ORM\ManyToMany(targetEntity="Product")
     * @Assert\Count(
     *   min=1, 
     *   max=10, 
     *   minMessage="Can't charge for an empty order", 
     *   maxMessage="Order is too large, ten items or fewer"
     * )
     */
    protected $products;
}