PHP判断是否是某个类的实例

<?php
namespace app\index\controller;

use think\Controller;
use think\Db;

class index extends Controller
{
    public function index()
    {
        $db = new Db();
        $this->test($db);
    }

    public function test(Db $param)	//是否是Db类的实例
    {
        var_dump($param);
    }
}

<?php
namespace app\index\controller;

use think\Controller;
use think\Db;
class index extends Controller
{
	$db = new Db();
	if($db instanceof Db){	//(instanceof)判断是否是Db类的实例
		echo 'Yes';
	}else{
		echo 'No';
	}
}