public static function composite_guid($guids)
    {
        if (!is_array($guids) || empty($guids)) {
            return '';
        }
        if (is_string($guids[0]) && strlen($guids[0]) == 16) {
            return implode('', $guids);
        }
        $validGuids = static::unsetInvalidGUIDs($guids);
        $composited = '';
        foreach ($validGuids as $guid) {
            $composited .= static::guid_bin($guid);
        }
        return $composited;
    }