Along with access control comes audit logging . Once you grant more users access to your site, you have a greater need to record the actions users have taken. For example, say your comic book collection is so extensive that you hire some folks to help you input books. Maybe there are consistent errors in the data entry. If you have audit trails, you can identify who is making the errors, and give them more training to input the books with fewer errors. Another common use for audit trails is to retrieve an item that has been accidentally deleted.
Download and unpack the
auditTrail extension from the Yii website (http://www.yiiframework.com/extension/audittrail/).