PHP ''Dynamic'' Checkboxes

I've tried to create list of users. In front of every user i have tried to place check box to check attendance. Unfortunately i don't succeed to create a "dynamic" one. Can somebody explain to me how to achive that type of list ? (to print checkbox infront of every registred user and print results)

Here is my code :

            <?php

                echo '<h2>Students:</h2>';

                $sql = "SELECT username FROM users WHERE user_type = 'user' ";

                $result = mysqli_query($db, $sql);

                if ($result){
                    while($user = mysqli_fetch_array($result)) {
                        echo $user['username'], '</br>';
                    }
                }

            ?>

        </div>