What are the potential pitfalls of using require_once and include_once in PHP?

Using require_once and include_once in PHP can lead to potential pitfalls such as increased server load due to repeated file inclusion checks and slower script execution. To avoid these issues, it is recommended to use require and include statements without the _once suffix, as they do not perform the additional check for file inclusion.

// Instead of using require_once or include_once, use require or include
require 'config.php';
include 'header.php';