什么可能导致$ _FILES ['file'] ['name']为空？

I have a form which includes a file upload. Everything in the form seems to be working fine except that the $_FILES['file']['name'] turns up empty.

HTML

<form ... >
<input class="file" type="file" name="file[]" />
<input class="file" type="file" name="file[]" />
<input class="file" type="file" name="file[]" />
</form>

PHP

foreach ($_FILES['file']['name'] as $index => $file) {
    // Handle file upload
}

I get an error saying that the index $_FILES['file'] is not defined. I've checked that file upload is enabled in PHP. What else could be causing this to turn up empty?

Is the enctype right?

Try

<form action="upload_file.php" method="post" enctype="multipart/form-data">
   <input class="file" type="file" name="file[]" />
   <input class="file" type="file" name="file[]" />
   <input class="file" type="file" name="file[]" />
</form>

Without enctype no files will be uploaded, so the $_FILES array will be empty.