class Single{
    //定义一个属性
    public $siteName;
    //本类的静态实例
    protected static $instance = null;
    //私有的构造方法
    private function __construct($siteName=‘‘){
        $this->siteName = $siteName;
    }
        
    
    //获取本类的唯一实例
    public static function getInstance($siteName=‘PHP‘){
        if(!self::$instance instanceof self){
            self::$instance = new self($siteName);
        }    
        return self::$instance;        
    }
}

//工厂模式
class Factory{
    //创建指定类的实例
    public static function create(){
        return Single::getInstance(‘HTML JS CSS‘);
    }

}

//注册树模式
class Register{
    public static $obj = [];
    public static function set($alias,$objects){
        self::$obj[$alias] = $objects;    
    }    
    public static function get($alias){
        return self::$obj[$alias];    
    }
    public static function _unset($aliass){
        unset(self::$obj[$alias]);    
    }
}

//注册一个hello类的实例，放到对象池
Register::set(‘hello‘,Factory::create());
//从对象池中获取hello类
$obj = Register::get(‘hello‘);
//查看属性
var_dump($obj->siteName);