Spørgsmål omkring glemt password

Kode 

<?php
 include_once('Connect2.php');
if(isset($_POST["send"]))
        {
            $pass_ny = rand();
            $nyt_passKODE = md5($pass_ny);
            if ($stmt = $db->mysqli->prepare('SELECT * FROM rytter WHERE ryttermail = ?')) { 

                
                $stmt->bind_param('s', $ryttermail);
                $ryttermail = $_POST["ryttermail"];
                $stmt->execute();
                $stmt->bind_result($ryttermail, $brugernavn);
                while ($stmt->fetch()) {
                   

 
                    $navn2 = $brugernavn;
                    $hilsen = "xxx.dk";
                    
                    $fra = "Ny Adgangskode til xxx.dk <" . "info@xxx.dk" . ">";
                    $til = $ryttermail;
                    $emne = "Ny adgangskode til xxx.dk";
                    
                    $besked = file_get_contents("glemt.php");
                    
                    $besked = str_replace("%%brugernavn", $rytternavn, $besked);
                    $besked = str_replace("%%pass", $pass_ny, $besked);
                    $besked = str_replace("%%hilsen", $hilsen, $besked);
                    
                    
                    $headers = "MIME-Version: 1.0 \r\n";
                    $headers .= "Content-type: text/html; charset=UTF-8\r\n";
                    $headers .= "From: " . $fra . "\r\n";
                    
                    
                    mail($til, $emne, $besked, $headers);
                            
                }
                $stmt->close();
            } else {
                echo 'Der opstod en fejl i erkl�¦ringen: ' . $this->mysqli->error;
            }
        if ($stmt = $this->mysqli->prepare('UPDATE rytter SET password=? WHERE ryttermail=?')) { 
            $stmt->bind_param('ss', $password, $email_indhold);
            $password = $nyt_passKODE; 
            $email_indhold = $_POST["ryttermail"];
            $stmt->execute();
            ?>
            <script language="javascript" type="text/javascript">  
                window.location.href = "/";  
            </script> 
            <?php
            $stmt->close();
        } else {
            echo 'Der opstod en fejl i erkl�¦ringen: ' . $this->mysqli->error;
        }
       }
php?>



<h1>Glemt kode til profil</h1>
    <form action="#" method="post">
        <table width="100%" cellpadding="2" cellspacing="1">
            <tr>
                <td>Email</td>
                <td><input type="email" name="ryttermail" maxlength="300"></td>
            </tr>
            <tr>
                <td></td>
                <td><input type="submit" name="send" value="Send email" class="KlikInput"></td>
            </tr>
        </table>
    </form>

Kode 

Fatal error: Call to a member function prepare() on null in xxx/glemt.php on line 8