This discsussion explors what Domain-Driven Design (DDD) is and how it can help PHP developers to write better code. DDD is an approach that places attention at the heart of the application, focusing on the complexity that is intrinsic to the business domain itself. It also distinguishes the core domain (unique to the business) from the supporting sub-domains (typically generic in nature, such as money or time), and places appropriately more of the design efforts on the core.
Video producer: PHP Roundtable
Further reading: An Introduction to Domain Driven Design