Add an nginx config gotcha to quick install wiki page

[gfdsa]

The thing that requires a special treatment is the usage of Apache's REDIRECT_URL instead of request uri. Given a working nginx config with fastcgi to php, one has to add a mapping of the original path before rewrite to php. My relevant working config looks like this:

    location / {
            root    /var/www/tonicdns/TonicDNS/docroot;
            try_files $uri $uri/ /dispatch.php;
    }
    location ~ \.php {
            root    /var/www/tonicdns/TonicDNS/docroot;
            fastcgi_pass   127.0.0.1:9001;
            include fastcgi_params;
            fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;
            fastcgi_param  REDIRECT_URL $request_uri;
    }