Lesson 15 - Interfaces and abstract classes in PHP

In the previous lesson, Interfaces in PHP, we introduced you to interfaces. Today, we are going to finish up with the theoretical part and start working with what are known as abstract classes.

By-passing multiple inheritance

As you already know, PHP can only inherit from a single class. Regardless, before we move on, let's get to the root of dealing with having to inherit from more than one object in a complex application.

Class hierarchy

If we want an object to inherit from two classes, we'd have to create a class hierarchy and inherit the object multiple times (Human -> Programmer -> PhpProgrammer):

class Human
{
    //...
}

class Programmer extends Human
{
    //...
}

class PhpProgrammer extends Programmer
{
    //...
}

In this case, PhpProgrammer technically inherits from both the Human and Programmer classes.

Interface delegating

In order to bypass the lack of multiple inheritance, we would have to use interfaces

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