public function filter($varname)
    {
        $val = $this->$varname;

        if (is_null($val) || $this->_sanitized) {
            return $val;
        }

        return is_array($val)
            ? filter_var_array($val, FILTER_SANITIZE_STRING)
            : filter_var($val, FILTER_SANITIZE_STRING);
    }