Easy understand Inheritance in php

class A {

public function myage() {

return ' age is 80';

}

class B extends A {

public function mysonage() {

return ' age is 50';

}

class C extends B {

public function mygrandsonage() {

return 'age is 20';

}

public function myHistory() {

echo "Class A " .$this->myage();

echo "Class B ".$this-> mysonage();

echo "Class C " . $this->mygrandsonage();

}

$obj = new C();

$obj->myHistory();

Output => Class A age is 80Class B age is 50Class C age is 20