Solid Principles in PHP – Dependency Inversion
Dependency Inversion states that high level modules should not depend upon low level modules. Instead, they should depend on abstractions and not concretions.
interfaces
Solid Principles in PHP – Interface Segregation
The letter I in SOLID stands for the interface segregation principle. The principle states that a client should not be forced to implement an interface that it doesn’t use.
Solid Principles in PHP – Liskov Substitution
The Liskov Substitution principle states that derived classes must be substitutable for their base classes. Meaning, every time you prepare a subclass, that subclass should be substituable in every place where the original class was accepted.
Solid Principles in PHP – Open-Closed
The O in SOLID represents the open-closed principle which states that entities should be open for extension but closed for modifications.
Solid Principles in PHP – Single Responsibility
A class should only have one responsibility and have only one reason to change.