如何编写上传和立即下载相同文件的php代码？

<form action="upload.php" method="post" enctype="multipart/form-data">
  <input type="file" name="fileToUpload" id="fileToUpload">
  <input type="submit" value="Upload File" name="submit">
</form>

<?php
if(isset($_POST["submit"])) {
  $targetDir = "uploads/"; // 上传文件保存的目录
  $targetFile = $targetDir . basename($_FILES["fileToUpload"]["name"]); // 上传文件的完整路径

  // 将上传的文件移动到目标位置
  if(move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $targetFile)) {
    echo "File uploaded successfully.";

    // 立即下载上传的文件
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename="'.basename($targetFile).'"');
    readfile($targetFile);
    exit;
  } else {
    echo "Error uploading file.";
  }
}
?>