Customizable 404 Error Pages for Specific Routes

You can extend the Error Handler and split HTTP errors into a handler in the controller.
As schematically (soorry, with phone):

PHP Code:

if ($exception->getCode() >= 400 && $controller->overWrite404) {
    return  $controller->overWrite404();
} 


if you need to process any response in 404, this is the work of Filters. Recognize the response and also replace the error

Simple CI 4 project for beginners codeigniter-expenses ( topic )