how to access function in PHP with Ajax feuture in AW?

i found the example in AW:
var req = new AW.HTTP.Request;
req.setURL('<url>');
req.response = function(text) {
alert(text); // do something with response here
};
req.request();

if the url is myscript.php and there's php function in the file.
how to access the function from AW like AJAX in the http://www.modernmethod.com/sajax/sajax-0.12/php/example_multiply.php

if we use this, we just access the url, not the function directly like in the http://www.modernmethod.com/sajax/sajax-0.12/php/example_multiply.php .may be we can use swicth() in php source to swicth the action to access the function. but i think it's more usefull and flexible if we can access the function directly. thanks for your sugestion.

var req = new AW.HTTP.Request;
req.setURL('/application/service.asmx');
req.setParameter('id', 12345); // set 'id' parameter
req.setParameter('filter', 'none'); // set 'filter' parameter
req.request(); // calls /application/service.asmx?id=12345&filter=none

AW does not include support for calling remote functions. AW.HTTP.Request class only allows to call a URL.