protected function copyCommand()
    {
        $sys = strtoupper(PHP_OS);

        if (substr($sys, 0, 3) == "WIN") {
            $copyCommand = "xcopy";
        } elseif ($sys == "LINUX") {
            $copyCommand = "cp";
        } else {
            $copyCommand = "cp"; // MacOS
        }

        return $copyCommand;
    }