文件输入类型的未定义索引[重复]

我有一个名为 文件 ,但在提交表单时,它会返回:

未定义的索引:文件位于C:\xampp\htdocs\Rehab\image\u upload\index。php第26行。

第26行 指的是: $file = $_FILES['file'];

这是我的html:

<form class="container-fluid d-flex justify-content-between" action="index.php" method="POST">
  <div class="col-md-4 mt-5 border-right pr-5 mr-5">
    <div class="form-group text-center">
      <legend class="display-4">Image Upload</legend>
    </div>
    <div class="form-group">
      <label for="title">Title</label>
      <input type="text" class="form-control" name="title" id="title" autocomplete="off">
    </div>
    <div class="form-group">
      <label for="image">Image</label>
      <input type="file" class="form-control" name="file" id="name">
    </div>
    <div class="form-group text-center">
      <button class="btn btn-outline-primary" name="submit">Post</button>
    </div>
  </div>
  <div class="col-md"></div>
</form>

下面是我的php代码:

if(isset($_POST['submit'])){
  $file = $_FILES['file'];

  if ($file['error'] > 0) {
    return echo "Error!";
  }

  if($error === 0){
    $name = $file['name'];
    $type = $file['type'];
    $size = $file['size'];
    $tmp_name = $file['tmp_name'];

    $name_explode = explode('.', $name);
    $file_ext = strtolower($name_explode[1]);

    $allowed = array('jpg','jpeg','png','gif');

    if(!in_array($file_ext, $allowed)) {
      return echo "Invalid file type!";
    }

    $new_name = uniqid('', true) . "." . $file_ext;
    $location = 'assets/images/' . $new_name;
    $query = $conn->query("INSERT INTO medicine VALUES ()");
    $move = move_uploaded_file($tmp_name, $location);
  }
}