ManyToMany config

Author

    /**
     * @var string
     *
     * @ORM\ManyToMany(targetEntity="Article", mappedBy="authors")
     */
    private $articles;
    
    
        /**
     * Constructor
     */
    public function __construct()
    {
        $this->articles = new \Doctrine\Common\Collections\ArrayCollection();
    }

    /**
     * Add article
     *
     * @param \AppBundle\Entity\Article $article
     *
     * @return Author
     */
    public function addArticle(\AppBundle\Entity\Article $article)
    {
        if (!$this->articles->contains($article)) {
            $this->articles[] = $article;
            $article->addAuthor($this);
        }
        return $this;
    }

    /**
     * Remove article
     *
     * @param \AppBundle\Entity\Article $article
     */
    public function removeArticle(\AppBundle\Entity\Article $article)
    {
        $this->articles->removeElement($article);
    }

    /**
     * Get articles
     *
     * @return \Doctrine\Common\Collections\Collection
     */
    public function getArticles()
    {
        return $this->articles;
    }

AuthorController

    /**
     * Displays a form to edit an existing author entity.
     *
     * @Route("/{id}/edit", name="author_edit")
     * @Method({"GET", "POST"})
     */
    public function editAction(Request $request, Author $author)
    {
        $deleteForm = $this->createDeleteForm($author);
        $editForm = $this->createForm('AppBundle\Form\AuthorType', $author);

        $originalArticles = new ArrayCollection();
        foreach ($author->getArticles() as $article) {
            $originalArticles->add($article);
        }
        $editForm->handleRequest($request);

        $em = $this->getDoctrine()->getManager();
        if ($editForm->isSubmitted() && $editForm->isValid()) {
            foreach ($originalArticles as $article) {
                if (false === $author->getArticles()->contains($article)) {

                    $article->getAuthors()->removeElement($author);

                    $em->persist($article);

                    // if you wanted to delete the Tag entirely, you can also do that
                    // $entityManager->remove($tag);
                }
            }

            $em->persist($author);
            $em->flush();

            return $this->redirectToRoute('author_edit', array('id' => $author->getId()));
        }

        return $this->render('author/edit.html.twig', array(
            'author' => $author,
            'edit_form' => $editForm->createView(),
            'delete_form' => $deleteForm->createView(),
        ));
    }