You have that, when a product is on development they can change its API anytime. This change is quite important though, its related on how to set the events of your form, for example, the useful beforeSubmit.
Uploading files in a webapp can be extremely tricky and sometimes the quickest way to do it is to store the file directly in the webserver or into a DNS (like Amazon S3) and then to save the link and the metadata inside a table in the DB. The thing is that you'll have to deal with file permissions, server storage, file management and so on (which is perfectly fine, by the way).
Here is a step by step To-Do list for Yii beginners. The list is an advice of what tutorials and documentation you can walk through to get a full understanding of the Yii Framework. These can be a help to learn Yii.
Countries sometimes change their laws pertaining to timezones and daylight saving times. This means that GMT+2 can be a different time this August compared to last August! However, by using php's DateTime class (instead of timestamps), we can do both "format" and "timezone" conversions on a single DateTime object (only 2 lines of code) for date, time, timestamp and datetime types - while php takes care of nightmares such as current and historical timezones and daylight saving times.