Описание тега extending-classes

You can extend a class to provide a more specialized behavior.

A class that extends another class inherits all the methods and properties of the extended class. In addition, the extending class can override the existing methods. Overriding a virtual method allows you to provide a different implementation for an existing method. This means that the behaviour of a particular method is different based on the object you're calling it on. This is referred to as polymorphism.

A class extends another class using the extends keyword in the class definition. A class can only extend one other class.

Example in PHP

class Hello {
    public function message() {
        return "Hello";
    }
}

class HelloWorld extends Hello {
    public function message() {
        return parent::message() . " World";
    }
}

$class = new HellowWord();
echo $class->message(); //"Hello World"

In this example we extend the class Hello, and override the function message.

Related tags: override method-overriding function-overriding