Book Image

Domain-Driven Design in PHP

By : Keyvan Akbary, Carlos Buenosvinos, Christian Soronellas
Book Image

Domain-Driven Design in PHP

By: Keyvan Akbary, Carlos Buenosvinos, Christian Soronellas

Overview of this book

Domain-Driven Design (DDD) has arrived in the PHP community, but for all the talk, there is very little real code. Without being in a training session and with no PHP real examples, learning DDD can be challenging. This book changes all that. It details how to implement tactical DDD patterns and gives full examples of topics such as integrating Bounded Contexts with REST, and DDD messaging strategies. In this book, the authors show you, with tons of details and examples, how to properly design Entities, Value Objects, Services, Domain Events, Aggregates, Factories, Repositories, Services, and Application Services with PHP. They show how to apply Hexagonal Architecture within your application whether you use an open source framework or your own.

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Table of Contents (24 chapters)
Title Page
Title Page
Credits
Credits
Foreword
Foreword
About the Authors
About the Authors
Acknowledgments
Acknowledgments
www.PacktPub.com
www.PacktPub.com
Customer Feedback
Customer Feedback
Dedication
Dedication
Preface
Preface
Free Chapter
1
Getting Started with Domain-Driven Design
Getting Started with Domain-Driven Design
Why Domain-Driven Design Matters
The Three Pillars of Domain-Driven Design
Considering Domain-Driven Design
The Tricky Parts
Strategical Overview
Related Movements: Microservices and Self-Contained Systems
Wrap-Up
2
Architectural Styles
Architectural Styles
The Good Old Days
Layered Architecture
Event Sourcing
Wrap-Up
3
Value Objects
Value Objects
Definition
Value Object vs. Entity
Currency and Money Example
Characteristics
Basic Types
Testing Value Objects
Persisting Value Objects
Security
Wrap-Up
4
Entities
Entities
Introduction
Objects Vs. Primitive Types
Identity Operation
Persisting Entities
Testing Entities
Validation
Entities and Domain Events
Wrap-Up
5
Services
Services
Application Services
Domain Services
Domain Services and Infrastructure Services
Testing Domain Services
Anemic Domain Models Vs Rich Domain Models
Wrap-Up
6
Domain-Events
Domain-Events
Introduction
Definition
Characteristics
Modeling Events
Doctrine Events
Persisting Domain Events
Publishing Events from the Domain Model
Spreading the news to Remote Bounded Contexts
Wrap-Up
7
Modules
Modules
General Overview
Leverage Modules in PHP
Bounded Contexts and Applications
Structuring Code in Modules
Wrap-Up
8
Aggregates
Aggregates
Introduction
Key Concepts
What Is an Aggregate?
Why Aggregates?
A Bit of History
Anatomy of an Aggregate
Aggregate Design Rules
Sample Application Service: User and Wishes
Transactions
Wrap Up
9
Factories
Factories
Factory Method on Aggregate Root
Factory on Service
Testing Factories
Wrap-Up
10
Repositories
Repositories
Definition
Repositories Are Not DAOs
Collection-Oriented Repositories
Persistence-Oriented Repository
Querying Repositories
Managing Transactions
Testing Repositories
Testing Your Services with In-Memory Implementations
Wrap-Up
11
Application
Application
Requests
Anatomy of an Application Service
Testing Application Services
Transactions
Security
Domain Events
Command Handlers
Wrap-Up
12
Integrating Bounded Contexts
Integrating Bounded Contexts
Integration Through the Data Store
Integration Relationships
Implementing Bounded Context Integrations
Wrap-Up
13
Hexagonal Architecture with PHP
Hexagonal Architecture with PHP
Introduction
First Approach
Repositories and the Persistence Edge
Decoupling Business and Persistence
Migrating our Persistence to Redis
Decouple Business and Web Framework
Rating an Idea Using the API
Console App Rating
Testing Rating an Idea UseCase
Testing Infrastructure
Arggg, So Many Dependencies!
Domain Services and Notification Hexagon Edge
Let's Recap
Hexagonal Architecture
Key Points
What's Next?
14
Bibliography
Bibliography
15
The End
The End

Chapter 6. Domain-Events

Software Events are things that happened in the system that other components might be interested in knowing about. PHP developers are generally not used to working with Events, which are not a feature in the language. However, it's more common to see how new frameworks and libraries embrace them to provide new ways of decoupling, reusing, and speeding up code.

Domain Events are Events related to Domain changes. Domain Events are things that happen in our Domain that Domain Experts care about.

In Domain-Driven Design, Domain Events are fundamental building blocks that help:

  • Communicate with other Bounded Contexts.
  • Improve performance and scalability, pushing for eventual consistency.
  • Serve as historical checkpoints.

Domain Events represent the essence of asynchronous communication. For more on this topic, we recommend the book Enterprise Integration Patterns:  Designing, Building, and Deploying Messaging Solutions by Gregor Hohpe and Bobby Woolf.

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