php - PHP- ZipArchive 0 字节文件

Question

我正在尝试将文件夹下载为 zip，但我总是得到一个 0 字节文件的 zip。我尝试了在互联网上找到的所有解决方案，但没有帮助。这是代码：

  $files= scandir($dir);
  $zip = new ZipArchive();


  $tmp_file = tempnam('.','');
  if (  $zip->open($tmp_file, ZipArchive::CREATE)===TRUE) {
    # loop through each file
    foreach($files as $file){

        # download file
        $download_file = file_get_contents($file);

        #add it to the zip
        $zip->addFromString(basename($file),$download_file);

    }

    # close zip
    $zip->close();

    # send the file to the browser as a download
    header("Content-disposition: attachment; filename=$nome_dir.zip");
    header("Content-length: " . filesize($tmp_file));
    header('Content-type: application/zip');
    readfile($tmp_file);
  }

我不明白我错在哪里