public function select_option($values, $selected_value) {
		$content = '';

		foreach ($values as $value => $title) {
			if (is_array($title)) {
				$label		= $this->_escape($value);
				$content	.= "<optgroup label=\"{$label}\">";
				$content	.= $this->select_option($title, $selected_value);
				$content	.= "</optgroup>";
			} else {
				$value		= $this->_escape($value);
				$title		= $this->_escape($title);

				$selected = '';
				if (is_scalar($selected_value) && $value == $selected_value) {
					$selected = ' selected="selected"';
				} elseif (is_array($selected_value) && in_array($value, $selected_value)) {
					$selected = ' selected="selected"';
				}

				$content	.= "<option value=\"{$value}\"{$selected}>{$title}</option>";
			}
		}

		return $content;
	}