Cal Evans has posted the first part of his look at DTAP - development, testing, acceptance and production - and how it applies to PHP development.
There are four primary systems that need to be set up and isolated. And they are described by the acronym DTAP-Development, Testing, Acceptance, and Production. One thing that has changed recently, though, is that these systems no longer have to mean separate hardware.
He gives an overview of each, setting out definitions to be used for the rest of the series with the next part discussing some of the "smaller moving pieces" of the process.