Preface

In 2014, after two years of reading about and working with Domain-Driven Design, Carlos and Christian, friends and workmates, traveled to Berlin to participate in Vaughn Vernon's Implementing Domain-Driven Design Workshop. The training was fantastic, and all the concepts that were swirling around in their minds prior to the trip suddenly became very real. However, they were the only two PHP developers in a room full of Java and .NET developers.

Around the same time, php[tek], an annual PHP conference, opened its call for papers, and Carlos sent one about Hexagonal Architecture. His talk was rejected, but Eli White — of musketeers.me and php[architect] fame — got in touch with him a month later wondering if he was interested in writing an article about Hexagonal Architecture for the magazine php[architect]. So in June 2014, Hexagonal Architecture with PHP was published. That article, which you'll find in the Appendix, was the origin of this book.

In late 2014, Carlos and Christian talked about extending the article and sharing all their knowledge of and experience in applying Domain-Driven Design in production. They were very excited about the idea behind the book: helping the PHP community delve into Domain-Driven Design from a practical approach. At that time, concepts such as Rich Domain Models and framework-agnostic applications weren't so common in the PHP community. So in December 2014, the first commit to the GitHub book repository was pushed.

Around the same time, in a parallel universe, Keyvan co-founded Funddy, a crowdfunding platform for the masses built on top of the concepts and building blocks of Domain-Driven Design. Domain-Driven Design proved itself effective in the exploratory process and modeling of building an early-stage startup like Funddy. It also helped handle the complexity of the company, with its constantly changing environment and requirements. And after connecting with Carlos and Christian and discussing the book, Keyvan proudly signed on as the third writer.

Together, we've written the book we wanted to have when we started with Domain-Driven Design. It's full of examples, production-ready code, shortcuts, and our recommendations based on our experiences of what worked and what didn't for our respective teams. We arrived at Domain-Driven Design via its building blocks — Tactical Patterns — which is why this book is mainly about them. Reading it will help you learn them, write them, and implement them. You'll also discover how to integrate Bounded Contexts using synchronous and asynchronous approaches, which will open your world to strategic design — though the latter is a road you'll have to discover on your own.

This book is heavily inspired by Implementing Domain-Driven Design by Vaughn Vernon (aka the Red Book), and Domain-Driven Design: Tackling Complexity in the Heart of Software by Eric Evans (aka the Blue Book). You should buy both books. You should read them carefully. You should love them.