$_FILES returns empty using DropzoneJS and Symfony 1.4

I've scoured through several SO and blog posts online but can't find something that works.

I'm trying to set up a simple HTML drag and drop form where users can upload several files at once via DropzoneJS.

HTML:

<form action='<?php echo url_for("@menu_basic_menu"); ?>' method="post" enctype="multipart/form-data" class="dropzone" id="basic_menu_dropzone"></form>

<button id="file_submit_btn" type="submit" form='basic_menu_dropzone' value="submit">SUBMIT</button>

Javascript:

jQuery(document).ready(function($) {
    Dropzone.autoDiscover = false;

    var dropzone = new Dropzone('#basic_menu_dropzone', {
        paramName: 'files',
        addRemoveLinks: true,
        uploadMultiple: true,
        autoProcessQueue: false,
    });

    $('#file_submit_btn').click(function() {
        dropzone.processQueue();
    });
});

Here you'll notice that I also set up a submit button such that we only start the upload process of the files on submit

PHP (snippet of actions.class.php):

public function executeBasicMenu(sfWebRequest $request) {
    if ($request->isMethod('post')) {
        print_r_tree($_FILES);
    }
  }

I have everything setup so that executeBasicMenu is properly fired on submit, but $_FILES always returns an empty array.

Notes:

• If I replace the dropzone form with a regular input type='file' tag then everything works, so my gut feeling is telling me my configuration with dropzone is wrong somewhere.
• I've stepped through the dropzone.js source code and it looks like right when it's about to send the data on line 1386: xhr.send(formData), formData is empty.

Any help is deeply appreciated!