PHP/SOAP Data being returned correctly, but PHP throwing an error as well

I am currently working with php and soap, and I have had to change the way i call the soap functions, which is fine, but I am getting a php error along with my Soap data, below is the snippet of code that is causing the issue.

    $params->loginID="xx";
    $params->password="xxxxx";
    $params->docType="Order";
    $params->partialDocID="";
    $ret = $client->Lookup($params);

The problem is the first line, or rather, whichever one of the $param lines i put first, it gives the following error:

Creating defa开发者_开发问答ult object from empty value

The data is being returned fine, but it is also returning that error, now I am not sure what the error means, I have looked it up and i have not found any information specific to what im doing.

To be honest, im not even sure what $params->xxx=xxx does...to me it looks like its storing a bunch of information and associations into a single string.

Initialize params: $params = new stdClass();