I am successfully connecting, using Microsoft C#, to a Microsoft web service. I have to supply a username, password (in the C# code); and install a certificate (in .cer format) into the "Root Certificate Authorities" section of the system's certificates.

How can I connect to such a web service in PHP? The reason I ask is that all methods I have seen (such as wsdl2php, which creates a SoapClient subclass), seem to assume various things, such as SSL certificate, SSL key file and SSL key passphrase.

So it all confuses me. I'm not sure what should go where. I'm not sure where my "root certificate authority" (the .cer file) should go, and where the username and password should go. Any ideas?