We have presented the object-oriented paradigm as the panacea for complex data structures, and even though we have shown that we can define objects with properties and methods, and it looks pretty and fancy, it is not something that we could not solve with arrays. Encapsulation was one feature that made objects more useful than arrays, but their true power lies in inheritance.
Inheritance in OOP is the ability to pass the implementation of the class from parents to children. Yes, classes can have parents, and the technical way of referring to this feature is that a class extends from another class. When extending a class, we get all the properties and methods that are not defined as private, and the child class can use them as if they were its own. The limitation is that a class can only extend from one parent.
To show an example, let's consider our Customer class. It contains the properties firstname, surname, email, and id. A customer is actually a specific...