insert subdomain into query

[NginxNewComer]

I have setup a wildcard subdomain server(many subdomains)
server {
  listen       80;
  server_name ~(?<subdomain>.*).localhost;
  ...
  ...
}

I want to make the subdomain apart of the query in the backend

when we visit http://clothes.localhost/ 
backend query
http://localhost/script.php?sd=clothes

or we visit http://jackets.localhost/large/blue/
backend query
http://localhost/script.php?sd=jackets&size=large&colour=blue

I have tried for 5 hours now, Modifying rewrite and return as many ways
possible, Multiple errors such as

rewrite ^ http://$subdomain.localhost/script.php?x=$subdomain permanent;

http://clothes.localhost/script.php/script.php/script.php/script.php/script.php/script.php/script.php/script.php/?sd=clothes?sd=clothes&sd=clothes?sd=clothes&sd=clothes?sd=clothes&sd=clothes?sd=clothes&
or
http://localhost/localhost/localhost/localhost/localhost

etc etc(I have tried many more tweaks but didnt record all as I went along)

Thanks in advance for any intention to help or answers given.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,245906,245906#msg-245906