Entities: Section & Category with table intermediare. Relation ManyToOne - OneToMany. How can I get the categories of a section ?

gistfile1.php

Class Intermediare: CategorySection
<?php
/**
* @ORM\Entity(repositoryClass="xxx\SectionBundle\Repositories\GiftCategorySectionRepositoryDoctrine")
* @ORM\Table(name="gift_category_section")
*/
class GiftCategorySection
        {
        /**
        * @ORM\Id
        * @ORM\ManyToOne(targetEntity="xxx\SectionBundle\Entity\GiftCategory", inversedBy="categories")
        * @ORM\JoinColumn(name="category_id", referencedColumnName="id")
        */	
        private $category;
        /**
        * @ORM\Id
        * @ORM\ManyToOne(targetEntity="xxx\SectionBundle\Entity\GiftSection", inversedBy="sections")
        * @ORM\JoinColumn(name="section_id", referencedColumnName="id")
        */	
        private $section;
        /**
        *
        * @ORM\Column(type="string")
        */
        private $title;
        [...]
?>

Class Category:

<?php    
/**
* @ORM\Entity(repositoryClass="xxx\SectionBundle\Repositories\GiftCategoryRepositoryDoctrine")
* @ORM\Table(name="gift_category")
*/
class GiftCategory
        {
        
        /**
        * @ORM\Id
        * @ORM\Column(type="integer")
        * @ORM\GeneratedValue(strategy="AUTO")
        */
        private $id;
       /**
        * @ORM\OneToMany(targetEntity="xxx\SectionBundle\Entity\GiftCategorySection", mappedBy="section")
        **/
        protected $sections;	
        [...]
?>

Class Section:
<?php      
/**
* @ORM\Entity(repositoryClass="xxx\SectionBundle\Repositories\GiftSectionRepositoryDoctrine")
* @ORM\Table(name="gift_section")
*/
class GiftSection
        {
        /**
        * @ORM\Id
        * @ORM\Column(type="integer")
        * @ORM\GeneratedValue(strategy="AUTO")
        */
        protected $id;
        /**
        * @ORM\OneToMany(targetEntity="xxx\SectionBundle\Entity\GiftCategorySection", mappedBy="section")
        **/        
        protected $sections;
        [...]
?>

           Category
+----+--------------------------+
| id | title                    |
+----+--------------------------+
|  1 | Love                     |
|  2 | Friendly                 |
+----+--------------------------+

               Section
+----+----------------------+
| id | title                |
+----+----------------------+
|  1 | Joke                 |
|  2 | Postal               |
|  3 | History              |
+----+----------------------+

              CategorySection
+----+-------------+------------+-----------------------+
| id | category_id | section_id | title                 |
+----+-------------+------------+-----------------------+
|  1 |           1 |          2 | joke of love          |
|  2 |           1 |          3 | all histories of love |
+----+-------------+------------+-----------------------+


Now the problem is... I want get the Categories of a Section, but how can I to do ?
Perhaps the relationship is bad ...
i.e I have a section with id=2 I want to know which categories there are to this section.
The query should get category 1...

Thanks in advance : )