PHP Request for SOAP XML - php

Question

i've got this XML and it works in soapUi
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:web="xxx" xmlns:data="xxx">
<soapenv:Header/>
<soapenv:Body>
<web:FindArticles>
<web:request>
<data:culture_id>de-DE</data:culture_id>
<data:vehicle_search_parameters>
<data:address>
<!--Optional:-->
<data:countries>
<!--Zero or more repetitions:-->
<data:country_id>D</data:country_id>
</data:countries>
<!--Optional:-->
</data:address>
<data:dealer_id>XXX</data:dealer_id>
<data:show_dealer_vehicles>true</data:show_dealer_vehicles>
</data:vehicle_search_parameters>
</web:request>
</web:FindArticles>
</soapenv:Body>
</soapenv:Envelope>
But I can not fugure out how to call it via PHP. I'm trying something like this, but get errors...
<?php
$wsdl = 'XXX';
$options = array(
'login' => 'XXX',
'password' => 'XXX',
'trace'=>true
);
$params = array(
'culture_id' => 'de-DE',
'country_id' => 'D',
'dealer_id' => 'XXX',
'show_dealer_vehicles' => true
);
try {
$soap = new SoapClient($wsdl, $options);
$data = $soap->FindArticles($params);
}
catch(Exception $e) {
die($e->getMessage());
}
var_dump($data);
die;
It looks, that there is some kind of nested functions - how have I call it via PHP? I've tried smth like $soap->FindArticles('request', $params), but it still does not work