CI 3 + Dropzone

You should be doing some basic error checking on the server too. Dropzone just grabs the file and sends it to the server. What happens after that is no longer it's concern. 




Replace this: 

PHP Code:

$this->upload->do_upload('file') 


With something like this and see what error is being reported.

PHP Code:

       if ( ! $this->upload->do_upload('file'))
        {
            //handle errors
            echo  $this->upload->display_errors();
        } else {
            //success, do something with the result!
            print_r($this->upload->data());
        }