public function single_button($url, $label, $method='post', array $options=null) {
        if (!($url instanceof moodle_url)) {
            $url = new moodle_url($url);
        }
        $button = new single_button($url, $label, $method);

        foreach ((array)$options as $key=>$value) {
            if (array_key_exists($key, $button)) {
                $button->$key = $value;
            }
        }

        return $this->render($button);
    }