It is pretty common to hear people talk about "SOLID code" in talks, blogs and podcasts these days. For the object-oriented programming novice who hears this term for the first time, the Wikipedia article gives a high-level overview, but advice and information about what ""SOLID"" really means on a practical level can be hard to come across. This talk aims to clarify what the SOLID principles are and how you can apply them in your work, with the aim of producing easier-to-maintain, de-coupled code with fewer smells. I'll show you PHP examples of each of the five SOLID principles, talk about when and how to implement them in your applications and give you a few other hints about ways you can improve your OOP design.