public function prompt($place, $html, $required = false)
    {
        switch ($place) {
            case 'info':
            case 'append':
                $this->prompt[$place] = $html;
                break;
            case 'prepend':
                $this->prompt['prepend'] = array('html' => $html, 'required' => (bool) $required);
                break;
        }
    }