如何显示所有用户，包括IP，排名和其他变量？

I am a starting PHP/sql-programmer, I am making a dashboard just for learning and I have a question. I want to let the page show something like this:

ID Name     IP            Rank
1   Willem   127.0.0.1 5
2   You       127.0.0.1 3

<table style="width:100%;color:white;">
          <tr>
            <th><center>ID</center></th><th>Naam:</th><th>IP:</th><th><center>Actie</center></th>
          </tr> <?php 
          $d = $con->query("SELECT * FROM tbl_users ORDER BY id DESC LIMIT 1000");
          while($r = $d->fetch_object()){ 
          ?>
          <tr>
            <td style="width:35px;text-align:center;"><?php echo $r->id; ?></td>
            <td><?php echo $r->userName; ?></td>
            <td><font color="red">Geblokkeerd</font></td>
            <td style="width:50px;text-align:center"><a href="./ase_users?type=edit&id=<?php echo $r->id; ?>">Bewerk</a></td>
          </tr>
          <?php } ?>
        </table

But if I put this code in de page, it gives me the following error:

Notice: Undefined variable: conn in /home/xxxxxxx/domains/xxxxxxx.nl/public_html/dashboard/beheer.php on line 133

Fatal error: Call to a member function query() on null in /home/xxxxxxxx/domains/xxxxxx.nl/public_html/dashboard/beheer.php on line 133

The dbconfig

 dbconfig.php
    <?php
    class Database
    {

        private $host = "localhost";
        private $db_name = "xxxxxx";
        private $username = "xxxxxx";
        private $password = "xxxxxx!";
        public $conn;

        public function dbConnection()
        {

            $this->conn = null;    
            try
            {
                $this->conn = new PDO("mysql:host=" . $this->host . ";dbname=" . $this->db_name, $this->username, $this->password);
                $this->conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);   
            }
            catch(PDOException $exception)
            {
                echo "Connection error: " . $exception->getMessage();
            }

            return $this->conn;
        }
    }
    ?>

Does anyone knows how to fix this?