One of the common tasks the web application might be required to perform, especially the app using some kind of a CMS, is to save the history of data changes. Your client for sure will want the answer to this simple question - If I mess this up or delete by accident can we bring it back? Well, DB backup is one thing and quick recovery is another - let's talk about latter one.

Suppose you have Products,Categories and each product belongs in many categories

In this wiki I will show you how to save/update a model with many related model For example: How to set a product to multiple categories only in one post form ?