What are the best practices for including header, main, and footer sections in PHP to create a professional-looking website?

To create a professional-looking website in PHP, it is best practice to separate the header, main content, and footer sections into separate files and then include them in your main PHP file using include or require statements. This modular approach helps keep your code organized and makes it easier to update and maintain your website.

// header.php
<!DOCTYPE html>
<html>
<head>
    <title>Your Website Title</title>
    <!-- Include CSS stylesheets and other meta tags here -->
</head>
<body>
    <header>
        <!-- Your header content goes here -->
    </header>

// main_content.php
<main>
    <!-- Your main content goes here -->
</main>

// footer.php
    <footer>
        <!-- Your footer content goes here -->
    </footer>
</body>
</html>
```

In your main PHP file, you can include these sections like this:

```php
<?php
include 'header.php';
include 'main_content.php';
include 'footer.php';
?>