I'm developing a web app where users will have their own sub-domain to login to and use the application. I'm running wordpress for the main website to manage the public / front end. Our application is developed in zend framework. The zf project is currently in a subfolder on the main server.

I'd like to place the zend framework project onto another server (different IP) and keep it separate from the the wordpress front end www.domain.com site.

The zf application server will run nginx. I'm not sure how to setup a server to run strictly sub domains. Setting up the virtual hosts in the configuration file is no problem. To give the users username.domain.com. But what about the main default configuration file? How would that be configured since the top level domain is technically another server (wordpress) on another IP?