データをDojoにプッシュするFiltering Select（コード付き）

I’m quite new to Zend & JSON, however I have the need to learn.
What I want to achieve is: having a Dojo filteringselect (with
autocomplete) control which is linked to zipcodes from a database
(and which keeps track of the ID, so I can store that ID as a FK in
another table (later on). The structure is MVC. I do get results
from the database, however I can’t seem to make it shine. Nothing
shows up in the filteringselect control. So basicly the structure
field of my database needs to get into the filteringsselect control
and keeping track of that id, because I need it later on as a FK in
another table. Please help me out!

表：

<?php
class Application_Model_Place extends FS_Model_Popo {
protected $_fields = array(
    'id'            => NULL, 
    'zip'      => NULL, 
    'name'          => NULL, 
    'up'            => NULL, 
    'structure'     => NULL);

protected $_primaryKey = array('id');
 }

形：

$place = new Zend_Dojo_Form_Element_FilteringSelect('Place');
$place->setLabel('Place')
    ->setAttrib('title', 'Add a place.')
    ->setAutoComplete(true)
    ->setStoreId('placeStore')
    ->setStoreType('dojox.data.QueryReadStore')
    ->setStoreParams(array('url' => '/graph/place/autocomplete'))
    ->setAttrib("searchAttr", "structure")
    ->setRequired(true);        

コントローラ：

class Graph_PlaceController extends Zend_Controller_Action {
public function autocompleteAction() {
    $this->_helper->viewRenderer->setNoRender();
    $this->_helper->layout->disableLayout();
    $structuur = $this->_getParam("structure", "");

    $results = FS_Model_Factory::getInstance()->place->autocomplete(array('structure like ?'=> "%".$structure."%"));
    $enc_res = array();
    foreach ($results as $value) {
        array_push($enc_res,$this->_helper->convert->toArray($value));
    }
    $this->_helper->json($enc_res);
    $data = new Zend_Dojo_Data('id', $enc_res);
    $this->_helper->autoCompleteDojo($data);
  }
}

json（$ enc_res）の例は次のようになります。

{"id":"235","zip":"3130","name":"Betekom","up":"BETEKOM","structure":"3130 Betekom"}, {"id":"268","zip":"3211","name":"Binkom","up":"BINKOM","structure":"3211 Binkom"},{"id":"377","zip":"3840","name":"Broekom","up":"BROEKOM","structure":"3840 Broekom"},{"id":"393","zip":"1081","name":"Brussel (Koekelberg)","up":"BRUSSEL (KOEKELBERG)","structure":"1081 BRUSSEL (KOEKELBERG)"},{"id":"421","zip":"1081","name":"Bruxelles (Koekelberg)","up":"BRUXELLES (KOEKELBERG)","structure":"1081 BRUXELLES (KOEKELBERG)"},{"id":"668","zip":"3670","name":"Ellikom","up":"ELLIKOM","structure":"3670 Ellikom"},{"id":"1236","zip":"3840","name":"Jesseren (Kolmont)","up":"JESSEREN (KOLMONT)","structure":"3840 Jesseren (Kolmont)"},{"id":"1275","zip":"3370","name":"Kerkom","up":"KERKOM","structure":"3370 Kerkom"}