When a class is defined by inheriting the existing function of a parent class, it is called inheritance. Here, the child class will inherit all or a few member functions and variables of a parent class. We can define an inherited class by using the extends keyword.

Inheritance has three types: Single, Multiple, and Multilevel Inheritance, but PHP only supports single inheritance, where only one class can be derived from a single parent class.

Example:

<?php  
    class exm {  
        public function func1()  
        {  
            echo "example of inheritance  ";  
        }     
    }  
    class exm1 extends exm {  
        public function func2()  
        {  
            echo "in php";  
        }     
    }  
    $obj= new exm1();  
    $obj->func1();  
    $obj->func2();  
?>

Output:

example of inheritance in php

Final Keyword

The final keyword can be used to prevent method overriding or to prevent class inheritance.

Example:

<?php
final class Employee {
  // some code
}
// This will result in error as the final keyword is used
class human extends Employee {
  // some code
}
?>