public function authenticate()
 {
     $login = $_REQUEST['login'];
     $password = md5($_REQUEST['password']);
     if ($login == '' || $password == '') {
         $user = new PEAR_Error('authentication_error_blank');
     } else {
         $user = new Administrator();
         $user->whereAdd("login = '******'");
         $user->whereAdd("password = '******'");
         $user->find();
         if ($user->N != 1) {
             $user = new PEAR_Error('authentication_error_invalid');
         } else {
             $user->fetch();
         }
     }
     return $user;
 }