Build around clear boundaries
Scalable PHP applications begin with simple, well-defined responsibilities. Keep request handling, business rules, persistence, and presentation separate so a change in one layer does not create a chain reaction elsewhere.
Practical principles
- Start with readable code and measured bottlenecks.
- Keep database queries predictable and indexed.
- Cache only the work that is proven to be expensive.
The goal is not complexity. It is a codebase that stays easy to reason about as it grows.