public function neighbouring_discussion_navigation($prev, $next) {
        $html = '';
        if ($prev || $next) {
            $html .= html_writer::start_tag('div', array('class' => 'discussion-nav clearfix'));
            $html .= html_writer::start_tag('ul');
            if ($prev) {
                $url = new moodle_url('/mod/forum/discuss.php', array('d' => $prev->id));
                $html .= html_writer::start_tag('li', array('class' => 'prev-discussion'));
                $html .= html_writer::link($url, format_string($prev->name),
                    array('aria-label' => get_string('prevdiscussiona', 'mod_forum', format_string($prev->name))));
                $html .= html_writer::end_tag('li');
            }
            if ($next) {
                $url = new moodle_url('/mod/forum/discuss.php', array('d' => $next->id));
                $html .= html_writer::start_tag('li', array('class' => 'next-discussion'));
                $html .= html_writer::link($url, format_string($next->name),
                    array('aria-label' => get_string('nextdiscussiona', 'mod_forum', format_string($next->name))));
                $html .= html_writer::end_tag('li');
            }
            $html .= html_writer::end_tag('ul');
            $html .= html_writer::end_tag('div');
        }
        return $html;
    }