Testing a web application may seem an hard task, but nowadays it is a fundamental part of the development process that ensures the application does not experience regressions, and it is free to grow incrementally. My point is that testability is a property which is desiderable not only for the ease of building an automated test suite, but also for the positive effects on the overall architecture that maintaining an application testable at the unit level produces. For example, being able to test a class in isolation is a sign of enough decoupling of it from the other collaborators, while keeping a limit on test cases length forces the production classes to be cohesive in functionalities.
PHP freelancer for several years, and now also an engineering student. I have a personal blog (http://giorgiosironi.blogspot.com) where you can find nearly two hundreds articles on web development topics published in the last year, particularly on the PHP platform. This blog raised the interest of many developers in the PHP field (I have about 1000+ feed subscribers and my articles got linked regularly on phpdeveloper.org.) I currently write also for php|architect’s website and the DZone network on their Web Builder zone.