Thanks Igor. The goal is to have Nginx do the load balancing for multiple servers that serve the same static content and php files.
Basically, I install Nginx in only one server that will be the load balancer, and PHP in all 4 servers that will contain the exact same thing (static files and php files):

upstream proxy {
server 1.localserverip:8000;
server 2.localserverip:8000;
server 3.localserverip:8000;
server 4.localserverip:8000;
}

upstream php {
server 1.localserverip:9000;
server 2.localserverip:9000;
server 3.localserverip:9000;
server 4.localserverip:9000;
}

Can you give an example how the configuration should look, while serving php and static files at the same time?
In other words, I want to be be able to output index.php from any of the servers, as well any static files. The Nginx balancer should be able to do this, right?