Matthias Willerich has posted a very complete guide to deploying PHP applications from a subversion repository with Vlad the Deployer (a Ruby-based deployment engine).

In my current day job I have to deploy a number of web apps every few weeks. The person I took over from did the whole thing in a manual and terribly cumbersome way. [...] In the following article, I'm going to describe how I went from there to deploying my Zend Framework-driven PHP apps with Vlad. To save yourself some time, feel free to skip the back story, the pre-requisite of installing ruby, gem and rake, or go straight to the deployment recipes.

He wanted a setup that would allow a "one-liner" for deployment, the ability to roll back and to have shares resources between releases. He walks you through the setup of all needed components, the configuration options and some example runs of his build/deploy process.