<?php

 class Person{

     private $userName;

     private $age;

     public function setAge($age){

         //$this->age = 16;

         //$this->age == private $age;

         $this->age = $age;

     }

     public function getAge(){

         return $this->age;

     }

     public function __set($key,$vule){

         $this->userName = $vule;

     }

     public function __get($key){

         return $this->userName;

     }

 }

 $p = new Person();

 // echo $p->userName;

 $p->setAge(16);

 echo $p->getAge();

 echo '<hr/>';

 $p->__set('userName', 'Clive');

 echo $p->__get('userName');