What are the potential pitfalls of including a file multiple times in PHP scripts?

Including a file multiple times in PHP scripts can lead to redeclaration errors if the file contains function or class definitions. To avoid this issue, you can use the `require_once` or `include_once` functions instead of `require` or `include` to ensure that the file is only included once.

// Include the file only once to prevent redeclaration errors
require_once 'file.php';