What are the potential pitfalls of including PHP sites within a webpage using the traditional header-site-footer method?

One potential pitfall of including PHP sites within a webpage using the traditional header-site-footer method is that it can lead to duplicate code and maintenance issues if changes need to be made across multiple pages. To solve this, you can create separate PHP files for the header, footer, and content sections, and include them using PHP's include function.

// header.php
<html>
<head>
    <title>My Website</title>
</head>
<body>

// footer.php
</body>
</html>

// index.php
<?php
include 'header.php';
?>

<h1>Welcome to my website!</h1>

<?php
include 'footer.php';
?>