What are best practices for including files in PHP to avoid errors like the one described in the forum thread?

The issue described in the forum thread is likely caused by including a file multiple times, leading to redeclaration errors. To avoid this, you can use PHP's `require_once` or `include_once` functions to include files only once in your code.

// Include the file using require_once to avoid redeclaration errors
require_once 'filename.php';