PHP5中的类与对象

<?php 
/** Define MyClass */ 
class MyClass 
{ public $public = ’Public’; 
protected $protected = ’Protected’; 
private $private = ’Private’; 
function printHello() 
{ echo $this->public; 
echo $this->protected; 
echo $this->private; 
} 
} 
$obj = new MyClass(); 
echo $obj->public; // // Works 
echo $obj->protected; // Fatal Error 
echo $obj->private; // Fatal Error 
$obj->printHello();// Shows Public, Protected and Priv 
class MyClass2 extends MyClass //Define MyClass2 
{// We can redeclare the public and protected method, but not private 
protected $protected = ’Protected2’; 
function printHello() 
{ echo $this->public; 
echo $this->protected; 
echo $this->private; 
} 
} 
$obj2 = new MyClass2(); 
echo $obj->public; // Works 
echo $obj2->private; // Undefined 
echo $obj2->protected; // Fatal Error 
$obj2->printHello();// Shows Public, Protected2, not Private 
?>