What are the best practices for including external scripts in a PHP project?

When including external scripts in a PHP project, it is important to follow best practices to ensure security and maintainability. One common approach is to use the `require_once` or `include_once` functions to include external scripts, as these functions will only include the file once to prevent any potential conflicts. Additionally, it is recommended to use absolute paths when including external scripts to avoid any path resolution issues.

// Example of including an external script using require_once with an absolute path
require_once __DIR__ . '/path/to/external/script.php';