Modification des relations entre User et Tag:

app/autoload.php

     'Assetic'          => __DIR__.'/../vendor/assetic/src',
     'Metadata'         => __DIR__.'/../vendor/metadata/src',
     'FOS'              => __DIR__.'/../vendor/bundles',
-    'Muzich'           => __DIR__.'/../vendor/src',
+    //'Muzich'           => __DIR__.'/../vendor/src',
 ));
 $loader->registerPrefixes(array(
     'Twig_Extensions_' => __DIR__.'/../vendor/twig-extensions/lib',

src/Muzich/CoreBundle/Entity/Tag.php

   protected $elements;
   
   /**
-   * @ORM\ManyToMany(targetEntity="Muzich\UserBundle\Entity\User", mappedBy="tags_favorites")
+   * @ORM\OneToMany(targetEntity="Muzich\CoreBundle\Entity\UsersTagsFavorites", mappedBy="tags_favorites")
    */
   protected $users_favorites;
   
       return $this->users_favorites;
   }
     
+
+    /**
+     * Add users_favorites
+     *
+     * @param Muzich\CoreBundle\Entity\UsersTagsFavorites $usersFavorites
+     */
+    public function addUsersTagsFavorites(Muzich\CoreBundle\Entity\UsersTagsFavorites $usersFavorites)
+    {
+        $this->users_favorites[] = $usersFavorites;
+    }
 }

src/Muzich/CoreBundle/Entity/UsersTagsFavorites.php

+<?php
+
+namespace Muzich\CoreBundle\Entity;
+
+use Doctrine\ORM\Mapping as ORM;
+
+/**
+ * @ORM\Entity
+ * @ORM\Table(name="users_tags_favorites")
+ */
+class UsersTagsFavorites
+{
+  
+  /**
+   * @ORM\ManyToOne(targetEntity="Muzich\UserBundle\Entity\User", inversedBy="tags_favorites")
+   * @ORM\JoinColumn(name="user_id", referencedColumnName="id")
+   */
+  protected $users_favorites;
+  
+  /**
+   * @ORM\ManyToOne(targetEntity="Muzich\CoreBundle\Entity\Tag", inversedBy="users_favorites")
+   * @ORM\JoinColumn(name="tag_id", referencedColumnName="id")
+   */
+  protected $tags_favorites;
+  
+  
+  /**
+   * @ORM\Id
+   * @ORM\Column(type="integer")
+   * @ORM\GeneratedValue(strategy="AUTO")
+   * @var type int
+   */
+  protected $id;
+  
+  /**
+   * @ORM\Column(type="integer")
+   * @var type int
+   */
+  protected $position;
+    
+
+  /**
+   * Set position
+   *
+   * @param integer $position
+   */
+  public function setPosition($position)
+  {
+      $this->position = $position;
+  }
+
+  /**
+   * Get position
+   *
+   * @return integer 
+   */
+  public function getPosition()
+  {
+      return $this->position;
+  }
+
+  /**
+   * Set users_favorites
+   *
+   * @param Muzich\UserBundle\Entity\User $usersFavorites
+   */
+  public function setUsersFavorites(Muzich\UserBundle\Entity\User $usersFavorites)
+  {
+      $this->users_favorites = $usersFavorites;
+  }
+
+  /**
+   * Get users_favorites
+   *
+   * @return \Muzich\UserBundle\Entity\User 
+   */
+  public function getUsersFavorites()
+  {
+      return $this->users_favorites;
+  }
+
+  /**
+   * Set tags_favorites
+   *
+   * @param Muzich\CoreBundle\Entity\Tag $tagsFavorites
+   */
+  public function setTagsFavorites(Muzich\CoreBundle\Entity\Tag $tagsFavorites)
+  {
+      $this->tags_favorites = $tagsFavorites;
+  }
+
+  /**
+   * Get tags_favorites
+   *
+   * @return Muzich\CoreBundle\Entity\Tag 
+   */
+  public function getTagsFavorites()
+  {
+      return $this->tags_favorites;
+  }
+  
+}

src/Muzich/UserBundle/Entity/User.php

 {
   
   /**
-   * @ORM\ManyToMany(targetEntity="Muzich\CoreBundle\Entity\Tag", inversedBy="users_favorites")
-   * @ORM\JoinTable(name="users_tags_favorites")
+   * @ORM\OneToMany(targetEntity="Muzich\CoreBundle\Entity\UsersTagsFavorites", mappedBy="users_favorites")
    */
   private $tags_favorites;
   
 
   public function __construct()
   {
-    $this->tags_favorites = new \Doctrine\Common\Collections\ArrayCollection();
+    $this->tags_favorites = new Doctrine\Common\Collections\ArrayCollection();
     parent::__construct();
   }
 
    *
    * @param Muzich\UserBundle\Entity\Tag $tagsFavorites
    */
-  public function addTag(\Muzich\UserBundle\Entity\Tag $tagsFavorites)
+  public function addTag(Muzich\CoreBundle\Entity\UsersTagsFavorites $tagsFavorites)
   {
       $this->tags_favorites[] = $tagsFavorites;
   }
       return $this->tags_favorites;
   }
   
+
+  /**
+   * Add tags_favorites
+   *
+   * @param Muzich\CoreBundle\Entity\UsersTagsFavorites $tagsFavorites
+   */
+  public function addUsersTagsFavorites(Muzich\CoreBundle\Entity\UsersTagsFavorites $tagsFavorites)
+  {
+      $this->tags_favorites[] = $tagsFavorites;
+  }
 }