How to setup a location to use $_SERVER['QUERY_STRING']

Hello,

I am trying to learn how to use NGINX to use a RESTFUL app, however I had some troubles to find any good tutorial about it. I have configured my site like this:
http://pastebin.com/tTqgRzjn

I would like to pass two parameter to $_SERVER['QUERY_STRING'], for example If I have this url:
index.php/user/myname/

Then, the query string would have two arguments, one of them would be "user" and the second one would be "myname".

I heard that this could be done using fastcgi_params, but I don't know how to use it. I did some searches in Google, but I didn't find any example to do it.

Could you explain me how to do it? Are there multiple approaches or is there only one way to do it? If there are multiple approaches, which one is the best to learn? Is there any book to learn about this?

Best regards.