需要更新选定的多行

Question

这是我的编码，我知道如何更新1行和所有行。我需要的是根据id

更新选定的多行

$db = new PDO('mysql:host=localhost;dbname=yumyum', 'username_here', 'password_here');
$id=$_POST['id'];
$ids = array();
foreach($ids as $id){
    $stmt = $db->prepare("SELECT Quantity, id FROM `food` WHERE `food`.`id` = :id");
    $stmt->bindParam(':id', $id);
    $stmt->execute();
    $row = $stmt->fetch();
    if($row){
        //uncomment to see $row content
        //var_dump($row);
        $rowId = (int)$row['id'];
        $rowQuantity = (int)$row['Quantity'];
        echo $rowQuantity;
        $ustmt = $db->prepare("UPDATE `food` SET `Quantity` = `Quantity` - 1 WHERE `food`.`id` = :id");
        $ustmt->bindParam(':id',$rowId);
        $ustmt->execute();
    }else{
        var_dump($stmt->errorInfo());
    }
}