Devise\Users\UsersRepository::retrieveCurrentUserId PHP Method

    public function retrieveCurrentUserId()
    {
        return $this->Auth->id();
    }

 /**
  * Convenience function to get current user's id
  *
  * @return integer
  */
 public function currentUserId()
 {
     return $this->UsersRepository->retrieveCurrentUserId();
 }