在Android应用程序中使用Web服务

I am getting into Android development and I have a question about calling a web service.

I have a web service written in PHP (lets say service.php).

To my knowledge in service.php I have to echo/print whatever I want the service call to return, is that correct?

Also, as this is a PHP service, is there a way to call a certain function (rather than using the querystring to decide).

Like in WCF I would call service.svc/GetUser/foobar (meaning get member foobar.