Symfony2 Passing ajax request data to a form rendering controller

I have a problem with a Symfony Form which I want to prefill based on which record is viewed on the page. The intention is to create a means for changing the record data. I navigate to the form page via javascript and send an ajax request to the same controller the form is rendered by.

This is part of the page used for viewing records:

    <input type="button" id="changeRecord" value="change"/>

    record id: <div id="recordID"> {{ record_id }} </div>

I access the record id through javascript/jQuery like this:

    var CssSelectors = new Array(
        "recordID"
    );

    function getCurrentRecordID() {
        return parseInt($.trim($("#" + CssSelectors[0]).text()));
    };

The button-code in javascript is the following:

    $('#changeRecord').click(function () {
        window.location.replace(Routing.generate(recordChangeRoute));

        $.ajax({
            url: Routing.generate(plasmidChangeAjaxRoute),
            type: "POST",
            data: {'recordID': getCurrentRecordID()}
    });

The Symfony Controller Action is the following:

public function changePlasmidRecordAction(Request $request) {
    $em = $this->getDoctrine()->getManager();
    $recordHandle = $em->getRepository('DataBundle:RecordClass');

    $AjaxRequest = Request::createFromGlobals();
    $RecordID = $AjaxRequest->request->get('recordID');

    $recordToUpdate = $recordHandle->findOneBy(array('id' => $RecordID));
    $updateForm = $this->createForm(new RecordClassType(), $recordToUpdate);
    $updateForm->handleRequest($request);

    if ($updateForm->isValid()) {
        $em->flush();
        return this->redirect($this->generateUrl('route_showRecord'));

    } else {
        return $this->render('DataBundle:RecordClass:updateRecord.html. twig',  
        array(
            'RecordID' => $RecordID,
            'form' => $updateForm->createView()
        ));
    }
}

What I am trying to achieve is:

• view a record


• go to prefilled form


• make changes and save

Viewing records, creating the form, persisting the changes to the database - all work. What does not work is accessing the needed ID inside the controller. I can access the ajax request data the way I try in an other controller action without problems. How is the "Form Request" interfering? Or is it? Do I have to use an Event Listener?

Any help is greatly appreciated, thanks in advance!