PHP get value from array->value - php

Question

I have this code:
function factuur_get_cardetails($form, &$form_state) {
//dd('getting cardetails');
$commands = array();
$i = 0;
foreach ($form_state['values']['field_invoice_line_deukendokter']['und'] as $line) {
if (count($line) > 1) {
// car
//dd($line);
// veld uitlezen
$kenteken = $line['field_invoice_carlicensenumber']['und'][0]['value'];
//dd($kenteken);
$url = 'https://api.datamarket.azure.com/opendata.rdw/VRTG.Open.Data/v1/KENT_VRTG_O_DAT?$filter=Kenteken%20eq%20%27'."$kenteken".'%27';
$xml = simplexml_load_file($url);
foreach($xml->entry as $entry){
$properties = $entry->content->children('http://schemas.microsoft.com/ado/2007/08/dataservices/metadata');
$auto = $properties->properties->children('http://schemas.microsoft.com/ado/2007/08/dataservices');
dd($auto->Handelsbenaming[0]);
$model = 'field_invoice_line_deukendokter[und]['.$i.'][field_invoice_carmodel][und][0][value]';
$id = "input[name='".$model."']";
$commands[] = ajax_command_invoke($id, 'val', array($auto->Handelsbenaming));
}
}
$i+=1;
}
return array('#type' => 'ajax', '#commands' => $commands);
}
The problem is when its gives me back [Object object] in my textbox while using
$commands[] = ajax_command_invoke($id, 'val', array($auto->Handelsbenaming));
Tho when i make a log using dd($auto) i get this
SimpleXMLElement Object
(
[Brandstofverbruikbuitenweg] => 3.20
[Brandstofverbruikgecombineerd] => 3.60
[Brandstofverbruikstad] => 4.30
[Catalogusprijs] => 20916
[Cilinderinhoud] => 1560
[CO2uitstootgecombineerd] => 95
[Datumaanvangtenaamstelling] => 2011-07-19T00:00:00
[DatumeersteafgifteNederland] => 2011-07-19T00:00:00
[Datumeerstetoelating] => 2011-07-19T00:00:00
[Eerstekleur] => GRIJS
[G3installatie] => N.v.t.
[Handelsbenaming] => DS3
)
So it somehow doesn't give me the value in "Handelsbenaming" and i don't know why.
Does anyone have an idea?
When i make a log dd($auto->Handelsbenaming);
it gives me this
SimpleXMLElement Object
(
[0] => DS3
)
but in my textbox it says [Object object] instead of DS3