config = $config;
                echo "我被实例化了";
    }
        //防止克隆对象
    private function __clone(){

    }
    static public function getInstance($config){
                //判断$instance是否是Uni的对象
                //没有则创建
        if (!self::$instance instanceof self) {
            self::$instance = new self($config);
        }
        return self::$instance;
        
    }
    public function getName(){
        echo $this -> config;
    }
}
$db1 = Uni::getInstance(1);
$db1 -> getName();
echo "
";
$db2 = Uni::getInstance(4);
$db2 -> getName();
?>