PhpCss\Ast\Visitor\Xpath::strtolower PHP Method

    private function strtolower($string)
    {
        if (is_callable('mb_strtolower')) {
            return mb_strtolower($string, 'utf-8');
        } elseif (class_exists('Transliterator', FALSE)) {
            return \Transliterator::create('Any-Lower')->transliterate($string);
        }
        return strtolower($string);
    }