Multiple PHP Websites

Hi

I think I need some help configurate nginx properly.
Im running multiple php sites in /usr/share/nginx/www/<subdirectory>, which works well with the nearly default configuration of nginx.

Now I want to make a new subpage with rewrite rules. I tried this configuration in a .conf file.. but it did not work.

# nginx configuration
autoindex off;

location /mysub/ {
if (!-e $request_filename) {
rewrite ^/mysub/(.+)$ /mysub/index.php?url=$1 break;
}
}

Thanks for your help.