最近需要使用PHP，所以我也只能把书拿出来看看，书是图灵的《PHP实战》，人民邮电出版的。
PHP中如何使用类
1: <?php
class Document{
protected $title;
private $text;
function __construct($title, $text) {
6: $this->title = $title;
7: $this->text = $text;
8: }
9: }
extends Document{
public $introduction;
function __construct($title, $text, $introduction) {
parent::__construct($title, $text);
14: $this->introduction = $introduction;
15: }
16: }
17: ?>