Parsing AJAX post data -- The Way

Just wondering what smart people do for parsing data sent by the Javascript XMLHTTP object--e.g., http.send("post",url,true)... In a normal form submit, the $_POST global nicely allocates form elements as array elements automatically. But with the AJAX way, the data get stuffed inside $HTTP_RAW_POST_DATA as a string, thereby making extraction more tedious. Any ideas? ...Rene