How to deal with duplication of functionality in the code?

Question

Yii

Hey! We cut products for internal corporate use. Sawing on Yii2.
It turns out like this: one saws the functionality of downloading files, components for notifications in telegrams, and so on. After half a year, the second one comes, sees or does not see that there is a ready-made functionality, or sees that it was written in haste and begins to saw everything of his own. And so every time.
Is there a way to do this all as someone automatically document? How to deal with this at all?
I come to the conclusion that for such products it is better to use a CMS like Drupal.