How can one ensure that any changes made to the navigation bar in a PHP forum do not affect the overall functionality of the site?

To ensure that changes made to the navigation bar in a PHP forum do not affect the overall functionality of the site, it is important to separate the navigation bar code from the rest of the site code. This can be achieved by creating a separate file for the navigation bar and including it in the main site template. By doing this, any changes made to the navigation bar will only affect the navigation itself and not impact the functionality of the rest of the site.

// navigation_bar.php

// Navigation bar code
<nav>
    <ul>
        <li><a href="index.php">Home</a></li>
        <li><a href="forum.php">Forum</a></li>
        <li><a href="contact.php">Contact</a></li>
    </ul>
</nav>
```

```php
// index.php

// Main site template
include 'navigation_bar.php';

// Rest of the site code
echo "Welcome to the site!";