Traits were introduced in PHP 5.4 (6 years ago) as a way to compose classes without relying on inheritance (in opposition to the ability to extends multiple classes like in C++). This feature of PHP…

The document discusses pursuing Domain-Driven Design practices in PHP. It covers building blocks like entities, value objects, aggregates, repositories, factories and services. It also discusses data modeling approaches like moving from active record to data mapper patterns. The document provides examples of implementing these concepts in PHP using annotations and libraries like Doctrine. It aims to help structure applications around the domain model and apply DDD practices like ubiquitous language in PHP projects.

Doctrine Object Relational Mapper Documentation: Association Mapping