What is Domain-Driven Design (DDD) in PHP?
Why Interviewers Ask This
Advanced questions like this reveal whether a candidate has internalized PHP deeply enough to make architectural decisions. Strong answers demonstrate both breadth and depth of experience.
Answer
Domain-Driven Design (DDD) is an approach to software development focused on modeling the core business domain in code. Key concepts: Entities (objects with identity that persists over time — e.g., User with ID), Value Objects (immutable objects defined by their value, not identity — e.g., Money(100, "USD")), Aggregates (cluster of objects treated as one unit with a root entity), Domain Events (something significant that happened in the domain), Repositories (abstract persistence per aggregate), Services (operations that do not belong to entities), and Bounded Contexts (explicit boundaries where a model applies). PHP frameworks like Symfony are commonly used for DDD because of their flexibility, while Laravel can also accommodate DDD with proper structuring.
Pro Tip
Demonstrate both theoretical understanding and practical experience. Say what it is, then give an example of how you actually used it in a PHP codebase.
Previous
What is PHP async programming with ReactPHP or Amp?
Next
What are intersection types in PHP 8.1?