PHP Application Lifecycle: Build vs. Deploy

Over the past few days, I've been playing with Phing, a build tool for PHP, similar to Ant for Java. I initially intended to use Phing to deploy a Web application I'm developing, but I've come to realize its power as a build tool while working on a set of PHP libraries as well. Through my time with the tool, I've realized the important distinction between a build tool, such as Phing, and a deployment tool.

Many articles and tutorials around the Internet tend to focus on using Phing for three things:

• Kicking off automated tests with PHPUnit
• Building API documentation with PHPDocumentor
• Deploying code to a Web server

While Phing is definitely suited for these tasks, and indeed comes with many built-in tasks for these exact purposes, it can be used — and is intended to be used — to do so much more.

In the PHP world, where code is not compiled, the primary purpose of a build tool is to prepare a code base for distribution. This usually means changing configuration files, cleaning out development-only artifacts, and packaging the code base in a neat little tarball, PEAR package, or other archive. While Phing and other build tools often have built-in support for simple deployments via rsync, scp, and other file transport mechanisms, they typically don't support truly robust deployment features.

In many environments, especially those with only a single Web server, the simple mechanisms provided by the build tools may be just fine. However, in more complex environments, these methods quickly break down, and deployment should be handled by a dedicated utility. That's not to say that Phing doesn't belong in these environments; to the contrary, the real power of Phing can shine through the most here. By taking the code base from its development environment, transforming it, testing it, and packing it, a build tool can pass off the prepared code to the deployment system with a higher level of code confidence than before.

Some time in the future, I'll discuss a little about how I'm managing my code with Phing, my deployment solutions, and introduce my other new friend, the Hudson continuous integration server.