if(mysql_num_rows($result) == 0){
            echo 'You have supplied a wrong user/password combination. Please try again.';
        }
        else{
            //set the $_SESSION['signed_in'] variable to TRUE
            $_SESSION['signed_in'] = true;

            //we also put the user_id and user_name values in the $_SESSION, so we can use it at various pages
            while($row = mysql_fetch_assoc($result)){
                $_SESSION['user_id']    = $row['user_id'];
                $_SESSION['user_name']  = $row['user_name'];
                $_SESSION['user_level'] = $row['user_level'];
            }
            echo 'Welcome, '. $_SESSION['user_name'].'. <br /><a href="index.php">Proceed to the forum overview</a>.';
        }