Inheritance

What is Inheritance

Inheritance is a very useful and popular concept that enhances the object-oriented programming experience. It allows a programmer to create and define classes that can inherit and build upon functionalities already present in existing classes without having to duplicate a lot of the code.

• Provides a way to create a new class from an existing class.

• The new class is a specialized version of the existing class.

• Allows the new class to override or redefine inherited methods from the existing class to perform differently than how they are defined in the existing class.

Terminology

• Base Class (or Parent): inherited by child class.
• Derived Class (or child): inherits from base class.

Characteristics

A derived class has:

• All members defined in the derived class.
• All ​members declared in the base class.

A derived class can:

• Use all public and protected members defined in the derived class.
• Use all public and protected members defined in the base class.
• Override an inherited member

A derived class cannot:

• Inherit constructors and destructors

Inheritance is one of the major reasons for using object-oriented programming in PHP.

Notation

Classes can inherit the properties and methods of another class using the keyword extends.

Let’s take a look at the notation below.