helper -> call to undefined function

Hello everyone.

Thank you for your insights and assistance.

The thing is, it had nothing to do with the helper file, but with the controller file name.
Since I uploaded my project to a Linux file system, which is case sensitive regarding file names, my controllers with composite names like "CheckOut" had to be renamed as "Checkout".

Anyways, everything is working just fine now.

Once again, thanks for all your help.