Switching from NuSoap to PHP5 Soap - need a jumpstart

Question

Here's the call I'm trying to make:

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"&gt;
<soap:Header xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"&gt;
    <urn:SessionHeader  xmlns:urn="http://www.mywebservice.com/webservices/SoapService" xmlns="http://www.mywebservice.com/webservices/SoapService" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"&gt;
        <urn:sessionId xmlns:urn="http://www.mywebservice.com/webservices/SoapService"&gt;LOGINTOKEN=your instance name</urn:sessionId>
    </urn:SessionHeader>
</soap:Header>
<soap:Body xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"&gt;
    <ns2:login xmlns:ns2="http://www.mywebservice.com/webservices/SoapService"&gt;
        <wsUser>
            <entityId>0</entityId>
            <password>your password</password>
            <username>your username</username>
        </wsUser>
    </ns2:login>
</soap:Body>

But I'm having trouble finding out how to set up the custom headers in PHP5's Soap. With nuSoap I could just put the whole thing into a variable and then use $client->setHeader($headerVar) but I can't find anything similar in PHP. If I could replicate this one call, I can figure the rest out. Any help would be appreciated!

Thanks in advance!

Update: I've gone through tutorial after tutorial, and read the PHP docs, but nothing seems to work. I can do what I want with curl (as well as nuSoap) but I thought the native PHP5 Soap would be easier and possibly more stable. I guess not...