Configuring NGINX to serve multiple webapps from different directories

Few days ago I had to add a wordpress installation within the same environment where a Codeigniter app was already running happily and undisturbed. It took me a while to figure out how to keep separate folders on the filesystem, and serve the blog from a subfolder of the main domain: it ended up that the solution is super simple, but apparently I am not the only one who had similar problems. Symptoms of a bad installation usually result in "no input file specified" messages or, even worse, downloading the php source code with all your precious database passwords shown in clear.

So the premise being:

there might be better and more elegant solutions, but this is working for me, including pretty permalinks on wordpress:

server {
    server_name your.domain.com;

    access_log /home/ubuntu/repo/logs/access.log;
    error_log /home/ubuntu/repo/logs/error.log;

    # main root, used for codeigniter
    root /home/ubuntu/repo/webapp;
    index index.php index.html;

    # links to static files in the main app, mainly for dev purposes as this is
    # unlikely to be triggered when using a CDN with absolute URLs to assets
    location ~* ^/(css|img|js|flv|swf)/(.+)$ {
        root /home/ubuntu/repo/webapp/application/public;
    }

    # most generic (smaller) request
    # most of the times will redirect to named block @ci
    location / {
        try_files $uri $uri/ @ci;
    }

    # create the code igniter path and perform
    # internal redirect to php location block
    location @ci {
        if (!-e $request_filename)
        {
            rewrite ^/(.*)$ /index.php/$1 last;
            break;
        }
    }

    # now the meaty part, execute php scripts
    location ~ \.php {
        include /etc/nginx/fastcgi_params;

        # default path of our php script is the main webapp
        set $php_root /home/ubuntu/repo/webapp;

        # but we might have received a request for a blog address
        if ($request_uri ~ /blog/) {
            # ok, this line is a bit confusing, be aware
            # that path to /blog/ is already in the request
            # so adding a trailing /blog here will
            # give a "no input file" message
            set $php_root /home/ubuntu/repo;
        }

        # all the lines below are pretty standard
        # notice only the use of $php_root instead of $document_root
        fastcgi_split_path_info ^(.+\.php)(/.+)$;

        fastcgi_param PATH_INFO $fastcgi_path_info;
        fastcgi_param PATH_TRANSLATED $document_root$fastcgi_path_info;

        fastcgi_param SCRIPT_NAME $fastcgi_script_name;
        fastcgi_param SCRIPT_FILENAME $php_root$fastcgi_script_name;

        fastcgi_pass unix:/var/run/php-fastcgi/php-fastcgi.socket;
        fastcgi_index index.php;
    }

    # now the blog, remember this lives in a sibling directory of the main app
    location ~ /blog/ {
        # again, this might look a bit weird,
        # but remember that root directive doesn't drop
        # the request prefix, so /blog is appended at the end
        root /home/ubuntu/repo;
        if (!-e $request_filename)
        {
            rewrite ^/(.*)$ /index.php/$1 last;
            break;
        }
    }
}

please feel free to add comments and suggestions, hope this helps.