Are there any best practices for designing a navigation system in PHP without using frames?

When designing a navigation system in PHP without using frames, it is important to create a modular and reusable navigation menu that can be included in each page of the website. This can be achieved by creating a separate PHP file for the navigation menu and using the include function to include it in each page. Additionally, using CSS for styling the navigation menu can help in creating a consistent look and feel across the website.

<!-- navigation.php -->
<ul>
    <li><a href="index.php">Home</a></li>
    <li><a href="about.php">About</a></li>
    <li><a href="services.php">Services</a></li>
    <li><a href="contact.php">Contact</a></li>
</ul>
```

In each page where you want to include the navigation menu, use the following code:

```php
<?php
include 'navigation.php';
?>