public function unset_hidden(string $id_imess, string $id_user){
    $cfg =& $this->class_cfg;
    if ( !empty($id_imess) && !empty($id_user) ){
      return !!$this->db->update_ignore($cfg['tables']['users'], [
        $cfg['arch']['users']['id_imessage'] => $id_imess,
        $cfg['arch']['users']['id_user'] => $id_user,
        $cfg['arch']['users']['hidden'] => 0,
        $cfg['arch']['users']['moment'] => date('Y-m-d H:i:s'),
      ], [
        $cfg['arch']['users']['id_imessage'] => $id_imess,
        $cfg['arch']['users']['id_user'] => $id_user
      ]);
    }
    return false;
  }