How can PHP developers ensure that included external content maintains the same design and formatting as the rest of the website?

When including external content in a PHP website, developers can ensure that it maintains the same design and formatting as the rest of the website by using CSS to style the content. By applying consistent styles to the included content, such as fonts, colors, and layouts, it can seamlessly blend in with the rest of the website.

// Example PHP code snippet to include external content with consistent styling

<div class="external-content">
    <?php
    $external_content = file_get_contents('http://example.com/external-content.html');
    echo $external_content;
    ?>
</div>

<style>
.external-content {
    font-family: Arial, sans-serif;
    color: #333;
    background-color: #f9f9f9;
    padding: 10px;
    border: 1px solid #ccc;
}
</style>