Наследование PHP

<?php
class MyExtClass extends MyClass {
 
  private $myName;
  private $myAdress;
 
function setMyName($myName){
  $this->myName=$myName;
}
  function print1 ($myName, $myAdress){
    echo "My Name is: {$this->myName}  ";
    echo "My Adress is: $myAdress \n";
 
  }
 
}
 
//=========================================================
// Реализация класса
$myClass = new MyExtClass();
$myClass->setMyName("ddddd");
$myClass->print1("sssss", "1111111111111111");
 
 
class MyClass {
 
  private $myName;
  private $myAdress;
/*
  function __construct (){
    $this->myName=$myName;
    $this->myAdress = $myAdress;
 
*/
 
function setMyName($myName){
  $this->myName=$myName;
}
  function print1 ($myName, $myAdress){
    echo "My Name is: {$this->myName} <br/>";
    echo "My Adress is: $myAdress \n";
 
  }
 
}
 
//=========================================================
 
 ?>