php web services

hi,
I m using nusoap library to call a webservice publishe in .net .it is not a normal webservice.it is a security enabled webservice.that means before peform any transaction we have to authenticate with it.they have provided simple vb.net code for authentication.so what I want to know is how to implement that authentication part using nusoap.vb.net code is as follows.

Dim token As UsernameToken
token=New UsernameToken("UserID", "Password",PasswordOption.SendHashed)
proxy.RequestSoapContext.Security.Tokens.Add(token)
ws.GetRoles();

// where ws is webservice object

thanks