class A
{
    //不允许类不直接实例化 或克隆
    private function __construct(){}
    private function __clone(){}
}

class B
{
    //不允许类不直接实例化 或克隆
    private function __construct(){}
    private function __clone(){}
}


class Factory
{
    public static function getInstance($class)
    {
        //类对象的获取方式通过工厂类 产生
        return new $class();
    }
}

$a = Factory::getInstance(‘A‘);
$b = Factory::getInstance(‘B‘);