Symfony\Component\Security\Core\Authentication\Token\UsernamePasswordToken::serialize() must return a string or NULL

[Raulken]

this in user bundle give to me this error

User.php public function serialize() { return serialize(array($this->facebookId, parent::serialize())); }

public function unserialize($data)
{
    list($this->facebookId, $parentData) = unserialize($data);
    parent::unserialize($parentData);
}

how i can fix?

[casoetan]

hey, have you fixed it / how did you fix it pls.