Continuous integration is not a new concept in software development, yet it’s a trending topic in the PHP community. Actually, the PHP development is evolving to a professional step. AGILE processes are spreading the web development world and so the continuous integration becomes a real business need.

This is a short and condensed introduction to the continuous integration in PHP. My next posts will cover deeply some parts. The main purpose of this blog is to provide keywords and concepts to ease your research.

I discovered the test-driven development more than 3 years ago in the symfony 1 documentation. This framework embeds a rudimentary, but efficient, test suite called lime. Frankly the tools don’t matter without the real will to improve your code quality.

The first question for many companies is: how much will it cost?
The long version : how much time/money will I have to spend to get a more reliable product or service? For this wrong paradigm, my answer is a reversed approach: could you estimate precisely the time/money lost without a continuous integration process?

To be honest, for lightweight projects, it’s still possible to evaluate the maintenance cost. But for huge projects using legacy-hard-coupled code, it’s a nightmare.

The customer, the boss or the developers love a bug tracker when it’s empty. The idea behind Test Driven Development (TDD) is to test your application before the release instead of fixing it after. Yes, it’s an extra cost on development estimated to 20% by Hugo Hamon from Sensio.But try to estimate the cost of your maintenance time and compare it. With the classic Blind Development you can’t predict it, since you have no reliable metrics on your application.

Test-driven development and continuous integration come to the rescue and don’t only allow a correct planning, it also reduces the number of “friday’s night emergency fix of the magic bug”. In short, everybody is happy : the customer, the boss, the wife and thus you too.

Unit test, functional test, acceptance test… These are answers which could and must be combined to match your need. Below is a quick summary and a tool kit for each purpose.

If you’re new to TDD or if you have short deadline : focus on unit tests. It’s the first mandatory step for the backend development which will reward you greatly. For php, consider phpUnit which is the actual standard, but keep also an eye on atoum. I believe that Behavior Driven Development should be use for acceptance, yet phpspec, mentioned by @andhos on twitter, offers a different approach : it’s a BDD framework focused on unit testing.

Sometimes you will need to test your whole application and probably by the presentation layer (i.e. almost like an user). Two solutions are available, first “Headless browser emulators” which are fast and reductive test focused on raw http output (See Goutte or Zombie.js). A second option are “Browser controllers” which simulate navigation with advanced js for example; you can use Sahi which replaced the famous Selenium.

To go further, look at Mink. It’s a web acceptance test framework based on the behavior test framework Behat (a port from cucumber in php). Mink provides an abstract layer for the web acceptance test which could be then executed by any tools mentioned above.

Beyond the test, lot of metrics can be collected about your code like cyclomatic complexity, duplicated code, coupled code… Furthermore, code standards should be controlled by a tool rather than an human eye. See Pdepend, phpmd (Mess Detector), phpCPD (duplicated code)…

Testing is one purpose, automating test is another one.
Let me introduce the gentleman called Jenkins (previously called Hudson), an open source java CI server. It’s the standard in this business. Sonar is another CI server, also in java, providing a nicer web GUI than Jenkins and maybe the nicest web GUI on the market for this concern. Finally, 2 new comers, first Travis CI a PaaS solution perfectly plugged with github, it’s a very sexy beta software. Second, mentioned in the comment by Pedro Mata-Mouros, an interesting solution called Cintient. It’s a beta but it seems to provide a cool UI with a minimal setup flow. I have to try it, yet expect a feedback on this blog soon.

For the deployment, only one answer : Capistrano. An unvaluable ruby tool for automated deployment processes.

Last thing, PHP is open-source like all the tools mentioned in this post. Most are hosted on github and provide a pear package. So now, you have no excuse to don’t start right now to improve your developments.

EDIT : thanks to the comments, I’ll added Cintient CI server.