Zend Framework - Dynamically add subforms to form using Ajax

/**
 * An extension to Jeremy Kendall's code (http://www.jeremykendall.net/2009/01/19/dynamically-adding-elements-to-zend-form/). Instead of adding single element, the code below attempts to dynamically add a set of elements to a form.

/*
index controller:

<?php

class IndexController extends Zend_Controller_Action
{
   public function indexAction ()
    {
        $form = new Application_Form_Dynamic();
        // Form has not been submitted - pass to view and return
        if (! $this->getRequest()->isPost()) {
            $this->view->form = $form;
            return;
        }
        // Form has been submitted - run data through preValidation()
        $form->preValidation($_POST);
        // If the form doesn't validate, pass to view and return
        if (! $form->isValid($_POST)) {
            $this->view->form = $form;
            return;
        }
        // Form is valid
        $this->view->form = $form;
    }

    public function newfieldAction ()
    {
        $this->_helper->layout->disableLayout();
        $ajaxContext = $this->_helper->getHelper('AjaxContext');
        $ajaxContext->addActionContext('addelm', 'html')->initContext();
        $id = $this->_getParam('id', null);
        $subform = new Zend_Form_SubForm();
        $subform->setIsArray(true);
        $subform->setName("child$id");
        $Element1 = $subform->createElement('text', "newfield$id");
        $Element1->setLabel("newfield$id")->setRequired(true);
        $subform->addElement($Element1);
        $Element1 = $subform->createElement('text', "nextfield$id");
        $Element1->setLabel("nextfield$id")->setRequired(true);
        $subform->addElement($Element1);
        $this->view->field = $subform;
    }
}
?>

Form class:
<?php
class Application_Form_Dynamic extends Zend_Form
{
    public function init ()
    {
        $element = new Zend_Form_Element_Text('name');
        $element->setRequired(true);
        $this->addElement($element);
        $this->addElement('hidden', 'id', array('value' => 1));
        $element = new Zend_Form_Element_Button('addentries',
        array('id' => 'add'));
        $element->setOrder(90);
        $this->addElement($element);
        $element = new Zend_Form_Element_Button('removeentries',
        array('id' => 'remove'));
        $element->setOrder(91);
        $this->addElement($element);
        $element = new Zend_Form_Element_Submit('submit');
        $element->setOrder(92);
        $this->addElement($element);
    }
    /**
     * After post, pre validation hook
     *
     * Finds all fields where name includes 'newName' and uses addNewField to add
     * them to the form object
     *
     * @param array $data $_GET or $_POST
     */
    public function preValidation (array $data)
    {
        // array_filter callback
        function findForms ($field)
        {
            // return field names that include 'newName'
            if (strpos($field, 'child') !== false) {
                return $field;
            }
        }
        $subForms = array_filter(array_keys($data), 'findForms');
        $children = array();
        foreach ($subForms as $subform) {
            if (is_array($data[$subform])) { // subforms added earlier will be passed to post as an array
                $children[$subform] = $data[$subform];
            }

        }
        foreach ($children as $key => $fields) {

            // strip the id number off of the field name and use it to set new order
            $order = ltrim($key, 'child') + 1;
            $this->addNewForm($key, $fields, $order);
        }
    }
    public function addNewForm ($form, $elements, $order)
    {
        $subform = new Zend_Form_SubForm();
        $subform->setIsArray(true);
        foreach ($elements as $key => $el) {
            $Element1 = $subform->createElement('text', $key);
            $Element1->setLabel($form . $key)
                ->setValue($el)
                ->setRequired(true);
            $subform->addElement($Element1);
        }
        $this->addSubForm($subform, $form, $order);
    }
}
?>
index.phtml:

<script type="text/javascript">

$(document).ready(function() {
    var id = $("#id").val();
    $("#add").on('click', function() {

        $.ajax({
              type: 'POST',
              data: "id=" + id,
              url: "<?php echo $this->url(array('action' => 'newfield', 'format' => 'html'));?>",
              success: function(data) {
                      $("#addentries-label").before(data);
                       $("#id").val(++id);
              },
              dataType: 'html'
            });
    });

    $("#remove").on('click', function() {
        // Get the last used id
          var lastId = $("#id").val() - 1;

          // Build the attribute search string.  This will match the last added  dt and dd elements.
          // Specifically, it matches any element where the id begins with 'newName<int>-'.
          searchString = '*[id^=child' + lastId + '-]';

          // Remove the elements that match the search string.
          $(searchString).remove();


          // Decrement and store id
          $("#id").val(--id);
    });

});
</script>
<div id="formdiv">
<?php
echo $this->form;
?>
</div>