What are the potential pitfalls of not using require_once/include_once in PHP?

The potential pitfall of not using require_once/include_once in PHP is that it can lead to the same file being included multiple times, causing redeclaration errors for functions or classes. To avoid this issue, it is recommended to use require_once or include_once to ensure that a file is only included once.

// Example of using require_once to include a file
require_once 'my_functions.php';