Explain advanced DDD tactical patterns and aggregate design in PHP.

DDD tactical patterns structure complex business domains using aggregates, entities, value objects, repositories, and domain services.

Domain-Driven Design becomes essential when business complexity exceeds infrastructure complexity.

Core tactical patterns:

Objects with identity over time.

Immutable descriptive structures.

Consistency boundaries enforcing invariants.

Persistence abstractions.

Business logic not belonging to entities.

Immutable business facts.

Aggregate design is one of the most critical DDD skills.…