PrestaShop has done much work to ensure 1.4 version modules backward compatibility with 1.5 version. For example, module configuration is saved automatically based on a selected store. However, if your module contains a Prestashop tab, get ready for trouble.
The thing is, any class, responsible for tab display in a back-office, extended the AdminTab class before. But in PrestaShop 1.5 the approach has changed. There should be an inheritance from the AdminController class. On the other hand, it allowed reaching the separation of logic and presentation. We don’t see echo in the tab class at last! All we need to do now is to use $this->fields_list variable in a constructor to pass an array of grid field values: