Stackoverflow 20124545

function zipDirectory($source, $destination, $flag = '') {
    if (!extension_loaded('zip') || !file_exists($source)) {
        return false;
    }
    $zip = new ZipArchive();
    if (!$zip->open($destination, ZIPARCHIVE::CREATE)) {
        return false;
    }
    $source = str_replace('\\', '/', realpath($source));
    if ($flag) {
        $flag = basename($source) . '/';
        //$zip->addEmptyDir(basename($source) . '/');
    }
    if (is_dir($source) === true) {
        $files = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($source), RecursiveIteratorIterator::SELF_FIRST);
        foreach ($files as $file) {
            $file = str_replace('\\', '/', realpath($file));
            if( in_array(substr($file, strrpos($file, '/')+1), array('.', '..')) ) continue;
            if (is_dir($file) === true) {
                $zip->addEmptyDir(str_replace($source . '/', '', $flag . $file . '/'));
            } else if (is_file($file) === true) {
                $zip->addFromString(str_replace($source . '/', '', $flag . $file), file_get_contents($file));
            }
        }
    } else if (is_file($source) === true) {
        $zip->addFromString($flag . basename($source), file_get_contents($source));
    }
    return $zip->close();
}
$zip_file = 'temp_' . $downloadID . '.zip';
zipDirectory($downloadID.'/', $zip_file, false);
header("Content-Type: application/zip");
header("Content-Length: ". filesize($zip_file));
header("Content-Disposition: attachment; filename=" . $zip_file);
readfile($zip_file);
unlink($zip_file);