<?php if ($result && $result->num_rows > 0): ?>
                    <?php while ($user = $result->fetch_assoc()): ?>
                        <tr>
                            <td><?php echo htmlspecialchars($user['id']); ?></td>
                            <td class="<?php echo ($user['is_admin'] ? 'admin-user' : 'normal-user'); ?>">
                                <?php echo htmlspecialchars($user['username']); ?>
                            </td>
                            <td><?php echo htmlspecialchars(date('Y-m-d', strtotime($user['register_date']))); ?></td>
                            <td><?php echo ($user['is_admin'] ? 'Yes' : 'No'); ?></td>
                        </tr>
                    <?php endwhile; ?>
                <?php else: ?>
                    <tr>
                        <td colspan="4">No users!</td>
                    </tr>
                <?php endif; ?>