public static function getById($commentId, $userId = null)
 {
     if ($comment = get_comment($commentId) and $comment->comment_type == self::COMMENT_TYPE) {
         if (empty($userId) or $comment->user_id == $userId) {
             $answer = new self($comment);
             if ($answer->getThread()) {
                 return $answer;
             }
         }
     }
 }