我有這樣的代碼,但是當我運行它時,它說對象不能轉換爲字符串。如何將類對象轉換爲字符串
$db = Database::getDB();
$query = "SELECT * FROM products WHERE productID = '$product_id'";
$result = $db->query($query);
$row = $result->fetch();
$category = CategoryDB::getCategory($row['categoryID']);
$fileName = new Product($category, $row['productCode']);
$dir = "../images/";
unlink($dir.DIRECTORY_SEPARATOR.$fileName);