private function _get_id_from_user(string $request, $params): ?string
  {
    if ( $this->id_user && $this->check() ){
      $sql = '
        SELECT `o`.`id`
        FROM bbn_observers AS `o`
          LEFT JOIN bbn_observers AS `ro`
            ON `o`.`id_alias` = `ro`.`id`
        WHERE `o`.`id_user` = ?
        AND (
          (
            `o`.`request` LIKE ?
            AND `o`.`params` '.($params ? 'LIKE ?' : 'IS NULL').'
          )
          OR (
            `ro`.`request` LIKE ?
            AND `ro`.`params` '.($params ? 'LIKE ?' : 'IS NULL').'
          )
        )';
       $args = [hex2bin($this->id_user), $request, $request];
       if ( $params ){
         array_splice($args, 2, 0, $params);
         array_push($args, $params);
       }
       return $this->db->get_one($sql, $args);
    }
    return null;
  }