Configure URL Rewrite in nginx

Im trying to set up URL Rewrites for my MVC Framework but as this is the first time i have used Nginx I am having a little trouble.

I have 2 access points for my application:

• /index.php
• /admin/index.php

I need to route the URL for those folders / access points to the according index file, for example:

• /admin/auth/login/ >>> /admin/index.php?/auth/login/
• /contact/ >>> /index.php?/contact/

This is what I have so far:

#Project
server {
listen 7000;
listen localhost:7000;

    location / {
        root   /srv/www/htdocs/ASDDL/;
        index index.php;
    }

    location /admin/ {
        root   /srv/www/htdocs/ASDDL/admin/;
        index index.php;
    }

    location ~ \.php$ {
        fastcgi_index    index.php;
        fastcgi_param  SCRIPT_FILENAME /srv/www/htdocs/ASDDL/$fastcgi_script_name;
        fastcgi_pass   127.0.0.1:9000;
        include fastcgi_params;
    }
}

Now as you can see that i think the problem lies with the following line:

fastcgi_param  SCRIPT_FILENAME /srv/www/htdocs/ASDDL/$fastcgi_script_name;

Where it's not routing to the admin folder because it tries to route to the root index.php file, can anyone shed some light on the correct way to do this?