What are the common pitfalls to avoid when including PHP files dynamically in HTML elements like cells of a table?

One common pitfall to avoid when including PHP files dynamically in HTML elements like cells of a table is not properly sanitizing user input, which can lead to security vulnerabilities such as code injection. To prevent this, always validate and sanitize any user input before including it in your PHP code.

// Example of sanitizing user input before including it in a table cell
$user_input = "<script>alert('Hello!');</script>";
$clean_input = htmlspecialchars($user_input);

echo "<td>" . $clean_input . "</td>";