SOAP api not accepting keys - php

Question

I'm trying to get data out of a SOAP API (complexType) but it's saying that my provided data is incorrect.
Errormessage I'm getting: "Wrong combination LINKCODE/LINKHASH"
(LINKCODE represents CompanyId & LINKHASH represents linkHash)
The weird thing is though, when I'm trying to get data using http://www.soapclient.com/soaptest.html, it works...
Are there things I have to provide such as schemes or encodings?
Anyway, this is my code:
<?php
include_once 'getArticles.class.php';
$objGetArticles = new getArticles();
$objGetArticles->CompanyId = 'xxx';
$objGetArticles->linkHash = 'xxx';
$objGetArticles->SyncOnlyGlobalPrices = 1;
$wsdl = "https://wcupwebservice.syscom.be/wsWCupDemo/wsWCupDemo.exe/wsdl/IwsWCup";
$client = new SoapClient($wsdl,
array (
'trace' => 1,
'exceptions' => 0,
'cache_wsdl' => WSDL_CACHE_NONE,
'keep_alive' => false
)
);
try {
$result = $client->getArticles(new SoapVar($objGetArticles, SOAP_ENC_OBJECT));
echo "<pre>";
print_r($result);
}catch (SOAPFault $f) {
echo $f->getMessage();
}catch (Exception $e) {
echo $e->getMessage();
}
getArticles.class.php:
<?php
class getArticles{
var $CompanyId;
var $linkHash;
var $SyncOnlyGlobalPrices;
}
Anybody know what to do here? I've spent so much time on this already.. Thanks!