Default.php

<?php
namespace BX\AppBundle\Controller;


/**
 * @Route("/item")
 */
class DefaultController extends Controller {
    /**
     * @Route("/new",name="item_new")
     * @Template()
     */
    public function newAction(Request $request) {
        $entity = new Item();
        $form = $this->createForm(new ItemType(), $entity);

        if ($request->getMethod() == 'POST') {
            $form->bind($request);
            if ($form->isValid()) {
                $em = $this->getDoctrine()->getManager();
                $em->persist($entity);
                $em->flush();
            }
        }

Item.php

<?php
namespace BX\AppBundle\Entity;

/**
 * Item
 *
 * @ORM\Table(name="item")
 * @ORM\Entity
 */
class Item
{
    /**
     * @var integer
     *
     * @ORM\Column(name="id_item", type="integer", nullable=false)
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    private $id;

    /**
     * @var string
     *
     * @ORM\Column(name="name", type="string", length=20, nullable=false)
     */
    private $name;

    /**
     * @var \Doctrine\Common\Collections\Collection
     *
     * @ORM\ManyToMany(targetEntity="\BX\AppBundle\Entity\Photo", mappedBy="item")
     */
    private $photo;

   
    public function __construct()
    {
        $this->photo = new \Doctrine\Common\Collections\ArrayCollection();
    }
    

    public function getId()
    {
        return $this->id;
    }


    public function setName($name)
    {
        $this->name = $name;
        return $this;
    }

    public function getName()
    {
        return $this->name;
    }

  
    public function addPhoto(\BX\AppBundle\Entity\Photo $photo)
    {
        $this->photo[] = $photo;
        return $this;
    }


    public function removePhoto(\BX\AppBundle\Entity\Photo $photo)
    {
        $this->photo->removeElement($photo);
    }

    public function getPhoto()
    {
        return $this->photo;
    }


}

ItemType.php

<?php

namespace BX\AppBundle\Form;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

class ItemType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('name', null, array('attr' =>array('class'=> 'input-xxlarge')))
            ->add('photo', 'collection', array(
                'label'  => 'Photos',
                'type' => new  \BX\AppBundle\Form\PhotoType(),
                'prototype' => true,
                'allow_add' => true,
                'allow_delete' => true,
            ))
        ;
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'BX\AppBundle\Entity\Item'
        ));
    }

    public function getName()
    {
        return 'bx_appbundle_itemtype';
    }
}

new.html.twig

<form action="" method="POST" {{ form_enctype(form) }} class="form-horizontal">
    {{ form_widget(form) }}
    <div class="control-group">
        <div class="controls">
            <input type="submit" class="btn btn-danger" value=">> Publish Item" />
        </div>
    </div>
</form>

<script type="text/javascript">
    var fotoCount = '{{ form.photo | length }}';
$(function() {
    $('#bx_appbundle_itemtype_photo').append('<a id="add-another-photo" href="">Add photo</a>');
    jQuery('#add-another-photo').click(function() {
        var photoList = jQuery('#bx_appbundle_itemtype_photo');


        var newWidget = photoList.attr('data-prototype');
        newWidget = newWidget.replace(/__name__/g, photoCount);
        photoCount++;

        // create a new list element and add it to the list
        var newLi = jQuery('<li></li>').html(newWidget);
        newLi.appendTo(jQuery('#bx_appbundle_itemtype_photo'));

        return false;
    });
});
</script>

Photo.php

<?php

namespace BX\AppBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Table(name="photo")
 * @ORM\Entity
 */
class Photo
{
    /**
     * @var integer
     *
     * @ORM\Column(name="id_photo", type="integer", nullable=false)
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    private $id;

    /**
     * @var string
     *
     * @ORM\Column(name="path", type="string", length=255, nullable=false)
     */
    private $path;

    /**
     * @var \Doctrine\Common\Collections\Collection
     *
     * @ORM\ManyToMany(targetEntity="\BX\AppBundle\Entity\Item", inversedBy="photo")
     * @ORM\JoinTable(name="photo_item",
     *   joinColumns={
     *     @ORM\JoinColumn(name="photo_id", referencedColumnName="id_photo")
     *   },
     *   inverseJoinColumns={
     *     @ORM\JoinColumn(name="item_id", referencedColumnName="id_item")
     *   }
     * )
     */
    private $item;


    public function __construct()
    {
        $this->item = new \Doctrine\Common\Collections\ArrayCollection();
    }
    

    /**
     * Get idFoto
     *
     * @return integer 
     */
    public function getId()
    {
        return $this->id;
    }

    public function setPath($path)
    {
        $this->path = $path;
    
        return $this;
    }

    public function getPath()
    {
        return $this->path;
    }

    public function addItem(\BX\AppBundle\Entity\Item $item)
    {
        $this->item[] = $item;
    
        return $this;
    }


    public function removeItem(\BX\AppBundle\Entity\Item $item)
    {
        $this->item->removeElement($item);
    }

    public function getItem()
    {
        return $this->item;
    }

       public function getAbsolutePath() {
        return null === $this->path ? __DIR__ . '/../../../../../web/assets/images/no-photo.png' : $this->getUploadRootDir() . '/' . $this->path;
    }

    public function getWebPath() {
        return null === $this->path ? 'assets/images/no-photo.png' : $this->getUploadDir() . '/' . $this->path;
    }

    protected function getUploadRootDir() {
        // the absolute directory path where uploaded
        // documents should be saved
        return __DIR__ . '/../../../../../web/' . $this->getUploadDir();
    }

    protected function getUploadDir() {
        // get rid of the __DIR__ so it doesn't screw up
        // when displaying uploaded doc/image in the view.
        return 'uploads';
    }

    /**
     * @Assert\File(maxSize="6000000")
     */
    private $file;

    /**
     * Get file.
     *
     * @return UploadedFile
     */
    public function getFile() {
        return $this->file;
    }

    private $temp;

    /**
     * Sets file.
     *
     * @param UploadedFile $file
     */
    public function setFile(\Symfony\Component\HttpFoundation\File\UploadedFile $file = null) {
        $this->file = $file;
        // check if we have an old image path
        if (isset($this->path)) {
            // store the old name to delete after the update
            $this->temp = $this->path;
            $this->path = null;
        } else {
            $this->path = 'initial';
        }
    }

    /**
     * @ORM\PrePersist()
     * @ORM\PreUpdate()
     */
    public function preUpload() {
        if (null !== $this->getFile()) {
            // do whatever you want to generate a unique name
            $filename = sha1(uniqid(mt_rand(), true));
            $this->path = $filename . '.' . $this->getFile()->guessExtension();
        }
    }

    /**
     * @ORM\PostPersist()
     * @ORM\PostUpdate()
     */
    public function upload() {
        if (null === $this->getFile()) {
            return;
        }

        // if there is an error when moving the file, an exception will
        // be automatically thrown by move(). This will properly prevent
        // the entity from being persisted to the database on error
        $this->getFile()->move($this->getUploadRootDir(), $this->path);
        //Redimensiona imagem
        $thumb = new \PHPThumb\GD(realpath($this->getUploadRootDir()) . DIRECTORY_SEPARATOR . $this->path);
        $thumb->adaptiveResize(175, 175);
        $thumb->save(realpath($this->getUploadRootDir()) . DIRECTORY_SEPARATOR . $this->path);

        // check if we have an old image
        if (isset($this->temp)) {
            // delete the old image
            unlink($this->getUploadRootDir() . '/' . $this->temp);
            // clear the temp image path
            $this->temp = null;
        }
        $this->file = null;
    }

    /**
     * @ORM\PostRemove()
     */
    public function removeUpload() {
        if ($file = $this->getAbsolutePath()) {
            unlink($file);
        }
    }
}

PhotoType.php

<?php
namespace BX\AppBundle\Form;

...

class FotoType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('file', 'file');
    }

    /**
     * Returns the name of this type.
     *
     * @return string The name of this type
     */
    public function getName()
    {
        return 'bx_appbundle_phototype';
    }
}