Doctrine2 m2m

Series.php

<?php

namespace Smartburk\Bundle\MainBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity(
 *     repositoryClass="Smartburk\Bundle\MainBundle\Entity\SeriesRepository"
 * )
 * @ORM\Table(name="series")
 */
class Series
{
    // ...

    /**
     * @ORM\ManyToMany(
     *     targetEntity="Smartburk\Bundle\MainBundle\Entity\Series",
     *     inversedBy="followers"
     * )
     * @ORM\JoinTable(name="user_following")
     */
    protected $following;

    /**
     * Add following
     *
     * @param Smartburk\Bundle\MainBundle\Entity\Series $following
     */
    public function addFollowing(\Smartburk\Bundle\MainBundle\Entity\Series $following)
    {
        $this->following[] = $following;
    }

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

    // ...
}

User.php

<?php

namespace Smartburk\Bundle\MainBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use FOS\UserBundle\Entity\User as BaseUser;

/**
 * @ORM\Entity
 * @ORM\Table(name="fos_user")
 */
class User extends BaseUser
{
    // ...

    /**
     * @ORM\ManyToMany(
     *     targetEntity="Smartburk\Bundle\MainBundle\Entity\Series",
     *     inversedBy="followers"
     * )
     * @ORM\JoinTable(name="user_following")
     */
    protected $following;

    /**
     * Add following
     *
     * @param Smartburk\Bundle\MainBundle\Entity\Series $following
     */
    public function addFollowing(\Smartburk\Bundle\MainBundle\Entity\Series $following)
    {
        $this->following[] = $following;
    }

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

    // ...
}