三个类概括PHP的五种设计模式

class people { 
private $name = ''; 
private $user = null; 
private function __constract($name){/*此处private定义辅助实现 单元素模式*/ 
$this->name = $name; 
} 
public static function instance($name){/*此方法实现 工厂模式*/ 
static $object = null;/*此变量实现 单元素模式*/ 
if (is_null($object)) 
$object = new people($name); 
return $object; 
} 
public function work_in($who=null) 
{ 
if (is_null($who)) echo 'error'; 
else { 
$this->user[] = $who;/*此数组变量实现 观察者模式*/ 
echo $who->work();/*此方法调用实现 策略模式*/ 
} 
} 
public function on_action($which=''){ 
if (empty($which)) echo 'error'; 
else { 
foreach ($this->user as $user) 
$user->action($which);/*此方法调用实现 命令链模式*/ 
} 
} 
} 
$people = people::instance('jack'); 
$people->work_in(new student); 
$people->work_in(new teacher); 
$people->on_action('eat'); 
class student { 
function work(){ 
echo '<br/>我是学生，朝九晚五。'; 
} 
function action($which){ 
if (method_exists($this, $which)) return $this->$which(); 
else echo 'you are wrong!'; 
} 
function eat(){ 
echo '<br/>我是学生，只能吃套餐。'; 
} 
} 
class teacher { 
function work(){ 
echo '<br/>我是老师，晚上备课最忙。'; 
} 
function action($which){ 
if (method_exists($this, $which)) return $this->$which(); 
else echo 'i can not do it!'; 
} 
function eat(){ 
echo '<br/>我是老师，可以每天吃大餐。'; 
} 
}