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 ?

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

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.