protected function alter_form_tag($matches)
    {
        $out    = $matches[0];
        $attrib = html::parse_attrib_string($matches[1]);

        if (strtolower($attrib['method']) == 'post') {
            $hidden = new html_hiddenfield(array('name' => '_token', 'value' => $this->app->get_request_token()));
            $out .= "\n" . $hidden->show();
        }

        return $out;
    }