How can PHP includes be effectively integrated into existing HTML structures, such as tables, without affecting the layout?

When integrating PHP includes into existing HTML structures like tables, it's essential to ensure that the included content doesn't disrupt the layout. One way to achieve this is by using PHP to include the content within table cells or other designated areas, making sure the included content aligns with the existing structure.

<table>
    <tr>
        <td>Header 1</td>
        <td>Header 2</td>
    </tr>
    <tr>
        <td><?php include 'content1.php'; ?></td>
        <td><?php include 'content2.php'; ?></td>
    </tr>
</table>