if ($u = $this->getRequestParameter('username'))
    {
      $u = "'%{$u}%'";
      $query->addWhere('u.username LIKE '.$u);
    }
    if ($e = $this->getRequestParameter('email'))
    {
      $e = "'%{$e}%'";
      $query->addWhere('u.email LIKE '.$e);
    }