public static function unicode_to_utf8($str)
    {
        if (extension_loaded('mbstring')) {
            return preg_replace_callback(
                '/\\\\u([0-9a-fA-F]{4})/',
                function ($match) {
                    return mb_convert_encoding(pack('H*', $match[1]), 'UTF-8', 'UCS-2BE');
                },
                $str
            );
        }

        return $str;
    }