zend framework 2 ajax request error

Im learning Zend framework 2. I found a post on how to make a Jquery modal window ajax request in zend. I made a little popup window with it where a user can add an album name and also an album type. When I'm running the scripts below without the Jquery modal window it saves perfectly to my database, but when I'm trying to do that via ajax nothing getting into the database. I started to look for the error and i found in the console when i want to post the form:

Failed to load resource: the server responded with a status of 500 (Internal Server Error) http://localhost/album/validatepostajax

but when I'm clicking on the URL it loads.

Any help is greatly appreciated.

Controller:

<?php 
namespace Album\Controller;

use Zend\Mvc\Controller\AbstractActionController;
use Zend\View\Model\ViewModel;

class AddNewAlbumController extends AbstractActionController {

public function savetodb($data)
{
    $mapper = $this->getServiceLocator()->get('Album/Mapper/Album');
    $mapper->insert($data);
}
protected function getForm()
{

    $form = $this->getServiceLocator()->get('Album\Form\AddNewAlbumForm');
    $form->setInputFilter(new \Album\Form\Filters\AddNewAlbumFormFilter());
    $form->setName('AlbumForm');

    return $form;
}

public function newalbumAction()
{
    $viewmodel = new ViewModel();
    $viewmodel->setTemplate('album/form/add-album.phtml');
    $form       = $this->getForm();
    $form->setHydrator ( new \Zend\Stdlib\Hydrator\Reflection () );

    $request = $this->getRequest();

    //disable layout if request by Ajax
    $viewmodel->setTerminal($request->isXmlHttpRequest());

    $is_xmlhttprequest = 1;
    if ( ! $request->isXmlHttpRequest()){
        //if NOT using Ajax
        $is_xmlhttprequest = 0;
        if ($request->isPost()){
            $form->bind ( new \Album\Entity\Album());
            $form->setData($request->getPost());
            $mapper = $this->getServiceLocator()->get('Album/Mapper/Album');
            if ($form->isValid()){
                $this->savetodb($form->getData());
            }
        }
    }

    $viewmodel->setVariables(array(
                'form' => $form,
                'is_xmlhttprequest' => $is_xmlhttprequest //need for check this form is in modal dialog or not in view
    ));

    return $viewmodel;
}

public function validatepostajaxAction()
{
    $form    = $this->getForm();
    $form->setHydrator ( new \Zend\Stdlib\Hydrator\Reflection () );
    $request = $this->getRequest();
    $response = $this->getResponse();

    $messages = array();
    if ($request->isPost()){
        $form->bind ( new \Album\Entity\Album());
        $form->setData($request->getPost());

        if ( ! $form->isValid()) {
            $errors = $form->getMessages();
            foreach($errors as $key=>$row)
            {
                if (!empty($row) && $key != 'submit') {
                    foreach($row as $keyer => $rower)
                    {
                        $messages[$key][] = $rower;
                    }
                }
            }
        }

        if (!empty($messages)){
            $response->setContent(\Zend\Json\Json::encode($messages));
        } else {
            $this->savetodb($form->getData());
            $response->setContent(\Zend\Json\Json::encode(array('success'=>1)));
        }
    }

    return $response;
}
}

View:

<script type="text/javascript">
var is_xmlhttprequest = <?php echo $this->is_xmlhttprequest; ?>;
var urlform           = '<?php echo $this->url('album\newalbum',
         array( 'action' => 'validatepostajax'));?>';
</script>

<?php echo $this->headScript()->appendFile($this->basePath() . '/js/ajaxform-up.js'); ?>

<?php
$form = $this->form;
$form->setAttribute('action', $this->url('album\newalbum',
         array( 'action' => 'newalbum'))
);
$form->prepare();
?>

<?php 
echo $this->form()->openTag($form); 
?>
<div class="element element_name">
<?php echo  $this->formlabel($form->get('name')).  $this->formelement($form->get('name'));?>
</div>
<div class="element element_type">
<?php echo  $this->formElement($form->get('type'));?>
</div>
<?php echo $this->formElement($form->get('submit')).$this->form()->closeTag(); ?>

Js:

$(function(){
$("form#AlbumForm").submit(function(){

    if (is_xmlhttprequest == 0)
        return true;

    $.post(urlform, { 'name' : $('input[name=name]').val(),
        'type' : $('select[name=type]').val()}, function(itemJson){

            var error = false;

            if (itemJson.name != undefined){

                $(".element_name").append("<div class = 'alert alert-error'>"+itemJson.name[0]+"</div>");

                error = true;

            }

            if (itemJson.type != undefined){

                $(".element_type").append("<div class = 'alert alert-error'>"+itemJson.type[0]+"</div>");

                error = true;

            }

            $( "winpopup" ).dialog( "option", "position",  { my: "center", at: "center", of: window } );
            if (!error){
                $("#winpopup").dialog('close');
                location.reload();
                if (itemJson.success == 1){
                    alert('Data saved');   
                }
            }

    }, 'json');

    return false;
});
});