<?php

namespace UCP\AbsenceBundle\Entity;

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

/**
 * @ORM\Entity
 * @ORM\Table(name="`User`")
 */
class User extends BaseUser
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\Column(type="string", length=15, nullable=true)
     */
    private $phone;
}

<?php

namespace UCP\AbsenceBundle\Entity;

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

/**
 * @ORM\Entity
 */
class User extends BaseUser
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\Column(type="string", length=15, nullable=true)
     */
    private $phone;
}

Remove table name quoting (seems useless)
Remove table name quoting (seems useless)
