單利 pdo 鏈接數據庫

class danli{
            public $db;
            protected static $ins=null;
                protected function __construct(){ 
                    
                    $servername = "localhost";
			        $username = "dbname";
			        $password = "cs.123456789";
			        try {
			            $this->db = new PDO("mysql:host=$servername;dbname=kuaijiezou", $username, $password);
			            //echo "Connected successfully"; 
			        }
			        catch(PDOException $e)
			        {
			            echo $e->getMessage();
			        }
                }

                public static  function getins(){
                    if(self::$ins ==null){
                       self::$ins = new self();
                    }
                    return self::$ins;
                }

         }
        $conn = danli::getins()->db;
        

$url = "SELECT id,breakfast,lunch,personal,isdayin FROM my_order";//訂單狀態已接單   支付狀態已支付   訂單狀態未打印
        $res = $conn->query($url)->fetch(PDO::FETCH_ASSOC);
        if($res['id']){
            $orderid = $res['id'];
            $isdayin = $res['isdayin'].$num;
            $v='';
            if($res['breakfast'] ==34){
                $v .= ",breakfast=36";
            }
            if($res['lunch'] ==34){
                $v .= ",lunch=36";
            }
            if($res['personal'] ==34){
                $v .= ",personal=36";
            }
               $v .= ",status=36";
           $sqlup = "UPDATE my_order SET isdayin=$isdayin$v WHERE id=".$res['id'];
            $count = $conn->exec($sqlup);