如何从Firefox 3中的HTML输入表单获取文件路径

<form action="upload.php" method="post" enctype="multipart/form-data">
 <label for="fileToUpload">选择文件：</label>
 <input type="file" name="fileToUpload" id="fileToUpload">
 <input type="submit" value="上传文件" name="submit">
</form>

<?php
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["fileToUpload"]["name"]);
$uploadOk = 1;
$imageFileType = strtolower(pathinfo($target_file,PATHINFO_EXTENSION));

if(isset($_POST["submit"])) {
  $check = getimagesize($_FILES["fileToUpload"]["tmp_name"]);
  if($check !== false) {
    echo "文件是一张图片 - " . $check["mime"] . ".";
    $uploadOk = 1;
  } else {
    echo "文件不是一张图片。";
    $uploadOk = 0;
  }
}

if (file_exists($target_file)) {
  echo "文件已经存在。";
  $uploadOk = 0;
}

if ($uploadOk == 0) {
  echo "文件上传失败。";
} else {
  if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)) {
    echo "文件：". htmlspecialchars(basename( $_FILES["fileToUpload"]["name"])). " 已经上传成功。";
  } else {
    echo "文件上传失败。";
  }
}
?>