你调用的对象是空的

It tells me that Object reference not set to an instance of an object, when trying to call this SOAP API.

I am doing this way

$client = new    SoapClient("http://gateway.XXXXXXX/gateway/api/creditcards/creditcardAPI.asmx?wsdl");

$params = array("clsCreditCardAPIBE" => (Object) array(
   "Username" => 'blabla',
   "Password" => "Barrel of Oil",
   "ProviderPIN" => 500,
   "AccountID" => 1234
    .......
));


$response = $client->__soapCall("Initiate_Deposit", $params);

What am i doing wrong?

You have to generate the client first, and then start using it

$client = new SoapClient("http://yourdomain.com?wsdl");