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.
You need to know how to program in PHP. You can find many tutorials on the web, or buy a book. If you'd like a book, I recommend Larry Ullman's books. Some people learn PHP from the PHP manual. Two web tutorials can be found on webmonkey and home&learn.
You need to know the basics of how Object Oriented Programming works. Same as above: use Google or buy a book. You need to read the PHP manual on OOP. It will take you a few hours. Another tutorial about OOP can be found here, and a video tutorial here.
It is very important to understand what the Model-View-Controller pattern means! If you don't, you will think Yii is chaos. As soon as MVC "clicks" in your mind, you will see the very logical pattern. Read up on one, two and three. You can also find an article here about Understanding MVC.
I highly recommend reading (or even rereading) the Getting Started with jQuery page from jQuery.com. These are some basics you need to know, since Yii uses jQuery as well. If you want to dive more into jQuery, I added some more links at the Extra's at the bottom.
The following is important to always remember: You always need to open the API pages on functions you're using. The descriptions of all functions of a language can be found here. The API docs are your memory, since your brain can't remember it ALL. ;) For PHP, use the search box on the top right of PHP.net. For jQuery, you can search the jQuery Docs. And here is the API for Yii 1.1 and for Yii 2, both of which have a search feature.
The Definitive Guide to Yii
The Definitive Guide to Yii is the central and most important learning resource for Yii. It is definitive and was written by the core Yii developers. It is available for Yii 1.1 and Yii 2. Just walk through all pages from top to the bottom. Tip: Also check out the comments on the bottom of the pages.
At some point while you read the Definitive Guide you'll want to get started with coding in Yii. If you begin with one of the conventional starting points then you stand a better chance of getting help when you need it.
Got confused what's happening?
You can trace all variables to the Yii Log to see what's in them. You can find more info here: How to log and debug variables using CWebLogRoute Irreplaceable for everyone to see whats happening! This is the best trick you ever learn:
There are a lot of good tips for Yii 1.1 in the Yii Application Development Cookbook. (If you buy it, check the errata section on their website.) Also check out the Yii Wiki and the Yii Class Reference. Tip: You can view Yii source code directly in the API docs. Also, the lookup/search box in there is invaluable.
There are a lot of extensions for Yii. These are extra "toolboxes", made by the Yii community, that you can re-use in your applications.
Return ... to the Source
To really understand Yii and use it most effectively, get into the habit of reading the Yii classes themselves. They are just PHP code that becomes part of your project. They are written using a simple, clear and consistent style. Remember to return to the source.
Basics - can take days, weeks or years. ;) Yii - Step 1 & 2, takes a few hours. The rest takes days, or a few weeks if you're doing things parttime. After all that, you should go into the depths of building your own custom Yii stuff!
Have fun with Yiiing! Kind regards, Jeroen
[Updated by thefsb/tom Oct 2014]