How To Modify Using My Changes Adddon

Hi,
Im triying to modify the file " app > Controllers > frontend > checkout.php"

But when i added the above path & checkout.php - it doesnt work

Could you please let anyone know how can i make it work please

Thank you in advance

You should use checkout.pre.php or checkout.post.php controller

You should use checkout.pre.php or checkout.post.php controller

Hi thank you for your help
but im not sure that i have mentined right,

Trying to modify the file "checkout.php" using addon called "my changes"
so if i want to make it work what path & file name do i have to add?

I have added below path and it wont work

design/backend/templates/addons/my_changes/overrides/app / Controllers / frontend / checkout.php

You cannot override controller, only template

To extend the controller use

app/addons/my_changes/controllers/frontend/checkout.pre.php

or

app/addons/my_changes/controllers/frontend/checkout.post.php

To override certain template use

design/themes/responsive/templates/addons/my_changes/overrides/views/checkout/checkout.tpl

More details can be found in the official documentation for developers