Create Album has many Photos using Doctrine

Album.php

<?php

namespace Admin\Entity;

use Doctrine\ORM\Mapping as ORM,
    Doctrine\Common\Collections\ArrayCollection;

use Zend\InputFilter\Factory as InputFactory;
use Zend\InputFilter\InputFilter;
use Zend\InputFilter\InputFilterAwareInterface;
use Zend\InputFilter\InputFilterInterface;

/**
 * Album
 *
 * @ORM\Table(name="bnc_album")
 * @ORM\Entity
 * @ORM\HasLifecycleCallbacks
 */
class Album implements InputFilterAwareInterface
{
    /**
     * @var integer
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    private $id;

    /**
     * @var string
     *
     * @ORM\Column(name="title", type="string", nullable=false)
     */
    private $tiltle;

    /**
     * @var string
     *
     * @ORM\Column(name="description", type="text", nullable=true)
     */
    private $description;

    /**
     * @var string
     *
     * @ORM\Column(name="main_photo", type="string", nullable=false)
     */
    private $main_photo;

     /**
     * @var \DateTime
     *
     * @ORM\Column(name="date", type="datetime", nullable=false)
     */
    private $date;

     /**
     * @param integer
     *
     * @ORM\Column(name="status", type="integer")
     */
    private $status;

    /**
     * @OneToMany(targetEntity="Photo", mappedBy="album_id")
     * @var Photo[]
     */
    protected $assignedPhotos = null;


    public function __get($property)
    {
        return $this -> $property;
    }

    public function __set($property, $value)
    {
        $this -> $property = $value;
    }

    public function __construct()
    {
        $this->assignedPhotos = new ArrayCollection();
    }

    public function assignedToPhoto($photo)
    {
        $this->assignedPhotos[] = $photo;
    }


    /**
    * Exchange array - used in ZF2 form
    *
    * @param array $data An array of data
    */
    public function exchangeArray($data)
    {
        $this->id          = (isset($data['id']))? $data['id'] : null;
        $this->description = (isset($data['description']))? $data['description'] : null;
        $this->tittle      = (isset($data['tittle']))? $data['tittle'] : null;
        $this->status      = (isset($data['status']))? $data['status'] : null;
        $this->main_photo  = (isset($data['main_photo']))? $data['main_photo'] : null;
        $this->date        = (isset($data['date']))? $data['date'] : null;
    }

    /**
    * Get an array copy of object
    *
    * @return array
    */
    public function getArrayCopy()
    {
        return get_object_vars($this);
    }

    /**
    * Set input method
    *
    * @param InputFilterInterface $inputFilter
    */
    public function setInputFilter(InputFilterInterface $inputFilter)
    {
        throw new \Exception("Not used");
    }

    /**
    * Get input filter
    *
    * @return InputFilterInterface
    */
    public function getInputFilter()
    {
        if (!$this->inputFilter) {
            $inputFilter = new InputFilter();
            $factory     = new InputFactory();

            $inputFilter->add($factory->createInput(array(
                'name'     => 'id',
                'required' => false,
                'filters'  => array(
                    array('name' => 'Int'),
                ),
            )));

            $inputFilter->add($factory->createInput(array(
                'name'     => 'description',
                'required' => true,
                'filters'  => array(
                    array('name' => 'StringTrim'),
                ),
                'validators' => array(
                    array(
                        'name'    => 'StringLength',
                        'options' => array(
                            'encoding' => 'UTF-8',
                            'min'      => 1,
                        ),
                    ),
                ),
            )));

            $inputFilter->add($factory->createInput(array(
                'name'     => 'name',
                'required' => true,
                'filters'  => array(
                    array('name' => 'StripTags'),
                    array('name' => 'StringTrim'),
                ),
                'validators' => array(
                    array(
                        'name'    => 'StringLength',
                        'options' => array(
                            'encoding' => 'UTF-8',
                            'min'      => 1,
                            'max'      => 255,
                        ),
                    ),
                ),
            )));

            $this->inputFilter = $inputFilter;
        }

        return $this->inputFilter;
    }
}

Photo.php

<?php

namespace Admin\Entity;

use Doctrine\ORM\Mapping as ORM;
    // Doctrine\Common\Collections\ArrayCollection;

use Zend\InputFilter\Factory as InputFactory;
use Zend\InputFilter\InputFilter;
use Zend\InputFilter\InputFilterAwareInterface;
use Zend\InputFilter\InputFilterInterface;

/**
 * Photo
 *
 * @ORM\Table(name="bnc_photo")
 * @ORM\Entity
 * @ORM\HasLifecycleCallbacks
 */
class Photo implements InputFilterAwareInterface
{
    /**
     * @var integer
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    private $id;


    /**
     * @var string
     *
     * @ORM\Column(name="description", type="text", nullable=true)
     */
    private $description;

    /**
     * @var string
     *
     * @ORM\Column(name="main_photo", type="string", nullable=false)
     */
    private $main_photo;

     /**
     * @var \DateTime
     *
     * @ORM\Column(name="date", type="datetime", nullable=false)
     */
    private $date;

     /**
     * Bidirectional - Many Photos are upload by one album (OWNING SIDE)
     *
     * @ManyToOne(targetEntity="Album", inversedBy="assignedPhotos")
     */
     private $album_id;


    public function __get($property)
    {
        return $this -> $property;
    }

    public function __set($property, $value)
    {
        $this -> $property = $value;
    }


    /**
    * Exchange array - used in ZF2 form
    *
    * @param array $data An array of data
    */
    public function exchangeArray($data)
    {
        $this->id          = (isset($data['id']))? $data['id'] : null;
        $this->description = (isset($data['description']))? $data['description'] : null;
        $this->tittle      = (isset($data['tittle']))? $data['tittle'] : null;
        $this->main_photo  = (isset($data['main_photo']))? $data['main_photo'] : null;
        $this->date        = (isset($data['date']))? $data['date'] : null;
        $this->album_id    = (isset($data['album_id']))? $data['album_id'] : null;
    }

    /**
    * Get an array copy of object
    *
    * @return array
    */
    public function getArrayCopy()
    {
        return get_object_vars($this);
    }

    /**
    * Set input method
    *
    * @param InputFilterInterface $inputFilter
    */
    public function setInputFilter(InputFilterInterface $inputFilter)
    {
        throw new \Exception("Not used");
    }

    /**
    * Get input filter
    *
    * @return InputFilterInterface
    */
    public function getInputFilter()
    {
        if (!$this->inputFilter) {
            $inputFilter = new InputFilter();
            $factory     = new InputFactory();

            $inputFilter->add($factory->createInput(array(
                'name'     => 'id',
                'required' => false,
                'filters'  => array(
                    array('name' => 'Int'),
                ),
            )));

            $inputFilter->add($factory->createInput(array(
                'name'     => 'description',
                'required' => true,
                'filters'  => array(
                    array('name' => 'StringTrim'),
                ),
                'validators' => array(
                    array(
                        'name'    => 'StringLength',
                        'options' => array(
                            'encoding' => 'UTF-8',
                            'min'      => 1,
                        ),
                    ),
                ),
            )));

            $this->inputFilter = $inputFilter;
        }

        return $this->inputFilter;
    }
}