think\Url::parseSuffix PHP Method

    protected static function parseSuffix($suffix)
    {
        if ($suffix) {
            $suffix = true === $suffix ? Config::get('url_html_suffix') : $suffix;
            if ($pos = strpos($suffix, '|')) {
                $suffix = substr($suffix, 0, $pos);
            }
        }
        return empty($suffix) || 0 === strpos($suffix, '.') ? $suffix : '.' . $suffix;
    }