Image: Pixabay SOLID is a mnemonic acronym for five object-oriented design principals that are intended to make software designs more understandable (see Wikipedia ). They were promoted by a chap called Robert C Martin who has been programming since before I was born and is an authority on writing clean code. Laravel is a PHP framework that implements the model-view-controller (MVC) pattern. A lot of people think that their responsibility for OOP design ends with adopting a framework, but actually Laravel is relatively un-opinionated on your OOP design and you still need to think about writing code that is testable and maintainable. The reason that SOLID principals matter becomes apparent when you work on a single project for a long time. If you're writing throwaway applications for clients that you never expect to work on again (presumably because the client won't hire you again) then the quality of your code doesn't matter. But if you're the guy stuck ...