将用户重定向到PHP-Mysql中由他/她的电话号码命名的文件夹

Question

I want to redirect a user to a folder named by his/her phone number(the folder created when the user signed up) and here is a part of my code:

if (count($errors) == 0) {
    $password = md5($password);
    $query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
    $results = mysqli_query($db, $query);




if (mysqli_num_rows($results) == 1) {
        $row=mysql_fetch_assoc($results);
        $folder = $row['phone'];
        $_SESSION['username'] = $username;
        $_SESSION['success'] = "You are now logged in";
        header("location:$folder"."/index.php");

It redirects the users to /index.php