protected function displayFooter()
    {
        ob_start();

        foreach ($this->extra_rows as $row) {
            $row->display();
        }

        $footer_content = ob_get_clean();

        if ($footer_content != '') {
            $tfoot_tag = new SwatHtmlTag('tfoot');
            if ($this->use_invalid_tfoot_ordering) {
                $tfoot_tag->class = 'swat-table-view-invalid-tfoot-ordering';
            }

            $tfoot_tag->setContent($footer_content, 'text/xml');
            $tfoot_tag->display();
        }
    }