When you have written and tested a Rails application, the next step is to host and deploy it to a Web server. The most common solution for this step is using the open source Apache HTTP Server for hosting (it's fast and works with PHP) and using Phusion Passenger to deploy the application to Apache (it makes scaling Apache easy).
Phusion Passenger is the most popular way to deploy Rails applications to Apache HTTP Server, because it offers multiple Apache scaling techniques. One of the biggest advantages of this approach is that PHP apps can run in the same server. So, if a person wants to run his or her WordPress blog in the Rails application, Apache makes that possible also.
In his Web Developer's Virtual Library (WDVL) tutorial, Saurabh Bhatia explains how to set up Phusion Passenger, configure Apache, and deploy multiple Rails applications on Apache.