Ib Quezada

I’ve been reading a lot about OOP in PHP, and I’ve noticed that these concepts may be confusing since they seem to work the same way.

Interfaces

Interfaces allow you to define methods a class implementing the interface and how to handle them.
All the methods specified in an interface must be implemented in a class.

interface GeometricShape {
    public function getArea();
    public function draw();
    // ...
}

Features of an Interface:

• A class can implement several interfaces.
• Interface constant cannot be overridden.
• Methods cannot contain code/logic.
• Methods must be public.
• Slower than abstract classes

Abstract Classes

Abstract classes look like interfaces but, this abstract classes can define methods, in other words, you can put a “default” logic to the abstract class methods.

abstract class GeometricShape {
    abstract protected function getArea() {
        // You can add some "default" code here
        return 0;
    }
}

Features of Abstract Classes

• A class can only extend one abstract class.
• Constrants can be overridden.
• Methods can contain logic (i.e. default code which can be overridden).
• Shared code can be in abstract classes.
• Fast.

There are more features you can find in an interface or an abstract class, however I don’t recall them right now

• http://php.net/manual/en/language.oop5.interfaces.php
• http://www.php.net/manual/en/language.oop5.abstract.php