Php-guide.7z (2026)

A class should have one, and only one, reason to change.

A class should not be forced to implement methods it does not use. php-guide.7z

Depend on abstractions (interfaces), not concrete implementations. A class should have one, and only one, reason to change

Objects of a superclass should be replaceable with objects of its subclasses without breaking the application. A class should have one

A high-level OrderManager should depend on a generic PaymentProcessorInterface rather than a specific PayPalPayment class. 📦 Understanding the .7z Context