下载多个zip文件

I want download multiple zip for multiple image at a time.But my code crate only one zip file for all image.

    foreach ($data as $key => $files) {
    /*$fileName="file.zip";*/
    $fileName = $key.'.zip';
    $tmpFile = tempnam('/tmp', '');
    $zip = new ZipArchive;
    $zip->open($tmpFile, ZipArchive::CREATE);
    foreach ($files as $file) {
        // download file
        $fileContent = file_get_contents($file);

        $zip->addFromString(basename($file), $fileContent);
    }
    $zip->close();

    header('Content-Type: application/zip');
    header('Content-disposition: attachment; filename='.$fileName);
    header('Content-Length: ' . filesize($tmpFile));
    readfile($tmpFile);
    echo $fileName;
    unlink($tmpFile);
}