我收到错误消息：

Object of class mysqli_result could not be converted to string

这是我的代码：

$username2 = htmlentities($_SESSION['user']['username'], ENT_QUOTES, 'UTF-8');

$con = mysqli_connect('localhost','root','','test');

$result = mysqli_query($con, "SELECT classtype FROM learn_users
                        WHERE username='$username2';");

echo "my result <a href='data/$result.php'>My account</a>";