why did not work input with div tag

I am working with laravel 5.6. and using dropzone with pragmatically. my dropzone div is like this,

 <div class="dropzone" id="my-dropzone"> 
    <div class="dz-message">
    
              <div class="col-xs-8">
                 <div class="message">
                    <p>Drop files here or Click to Upload</p>
                 </div>
              </div>
    </div>
    <div class="fallback" id="fallback">
        <input type="file" name="file" multiple>
        
    </div>
</div>

and

Dropzone.autoDiscover = false;

// Dropzone class:
var myDropzone = new Dropzone("div#my-dropzone", { url: '/form'});

and My image store Controller is

 public function store(Request $request)
    {
       

    $photos = $request->file('file');
 dd($photos);
        if (!is_array($photos)) {
            $photos = [$photos];
        }
 
        if (!is_dir($this->photos_path)) {
            mkdir($this->photos_path, 0777);
        }
        
 
        for ($i = 0; $i < count($photos); $i++) {
            $photo = $photos[$i];
            $name = sha1(date('YmdHis') . str_random(30));
            $save_name = $name . '.' . $photo->getClientOriginalExtension();
            $resize_name = $name . str_random(2) . '.' . $photo->getClientOriginalExtension();
 
            Image::make($photo)
                ->resize(250, null, function ($constraints) {
                    $constraints->aspectRatio();
                })
                ->save($this->photos_path . '/' . $resize_name);
 
            $photo->move($this->photos_path, $save_name);
 
            $upload = new Upload();
            $upload->filename = $save_name;
            $upload->resized_name = $resize_name;
            $upload->original_name = basename($photo->getClientOriginalName());
            $upload->save();
        }
        return Response::json([
            'message' => 'Image saved Successfully'
        ], 200);
}

but when I use input with this div

<div class="fallback">
        <input type="file" name="file" multiple>
        
    </div>

multiple images uploading is not working dd(photos); is occurred null value. but without above div class single image upload is working. what is the error how can fix this problem?