When to put code in Controller and when in Model

Create a new layer in folder Services, Helpers...:
class OrderService or class OrderCreator
Add a method to it with your desired parameters:

public function createOrderFromUser($user, $order, $file, $options, ...)

and inside you work with several models (namely with a database), upload a picture, check validation and so on. 

In response, return either true/false or a new order with a picture. In controller call:

PHP Code:

 $orderHelper = new OrderService();
 $order = $orderHelper->createOrderFromUser(...); 


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