What You Need to Know Before You Start!
Yii2 takes "full advantage" of some of the "newer" (I know it's been out a long time, but some of us haven't had the liberty to use it) capabilities of PHP - namely (pun intended) requiring PHP5.4 as a minimum, and using Composer to create new Yii applications. They've also switched out the standard PHPUnit tests in the application for Codeception.
If you're at all like me and have been nose to the grindstone on servers locked into PHP in the 5.3 (or lower) family, this will come as quite a system shock, even when you know it's coming ... I'm ashamed to admit that I looked at an array in 5.4 syntax and tried to figure out why there was JSON code in my PHP file.
So, forget all the implementation differences between Yii 1.1 and Yii 2.0 for now -- If you're not already fluent with PHP 5.4, Composer and Codeception, spend a week getting there.
Composer - PHP Package ManagerThe documentation for installing Composer is very straightforward and can be found at http://getcomposer.org
Getting it running on my Ubuntu VM was very straight forward, but on my Macbook I had to go through quite a bit of shenanigans to get XCode updated (required by Composer). I ended up having to uninstall and reinstall XCode before Composer would work properly there. Though the PHP upgrade on the Macbook trumped the PHP upgrade on the Ubuntu machine. So scratch off an evening just getting Composer running smoothly across the board. I believe this will be the preferred method of releasing extensions, etc. so if you're planning to move in that arena and aren't already familiar with this, time to read up.
I'm still figuring out all the basics for it, but it seems like a very handy way to keep packages maintained, and I'm looking forward to really becoming familiar with it.
PHP 5.4: Namespaces and ArraysOh my. So, the namespaces take a lot of getting used to, seeing all the /path/to/myClass::$variable and it seems like it takes up a lot more characters to do something very simple. Lots of power there though, and once you get used to reading it and writing it that way, it will become second nature. For the full list of what's dramatically different, check out the PHP 5.4 migration guide.
Arrays can now be generated with short array tags, and you'll find this extensively in the Yii2 code.
$config = array('something'=>'else','sub'=>array('marine'=>'sandwich'));becomes
$config = ['something'=>'else','sub'=>['marine'=>'sandwich']];Much more concise, but will definitely throw you for a loop the first time you see it. It's going to be a while before I can read that as quickly as I can the old style.
CAUTION: Once you start looking ahead, it'll be hard to go back to the old 5.3 ways -- so be sure you're ready!
Codeception Testing FrameworkI haven't looked into Codeception very far yet, but it essentially runs all the tests from a 'story' point of view. This is my personal homework for the next few days. If you're as dependent on TDD as you should be, you will want to brush up on this before diving in.
Finally, my favorite ...
Bootstrap 3.1.0The new sample applications implement Bootstrap 3.1.0 which has been changed significantly from the Bootstrap v2. Bootstrap 3 is designed not just to be mobile responsive, but mobile first. If you're used to using any of the other CSS libraries or the v2 flavors of Bootstrap, spend a little time getting familiar with the changes that have been implemented in the v3 line. It's well worth it.
Once you're FULLY familiar with the syntax changes for 5.4 / 5.5 (whatever your flavor), and Namespaces no longer throw you for a loop, and Composer is installed and functional, it's finally time to start reading
Upgrade from v1 on the Yii2 docs.
I should also mention, my beloved "yiic" command is no more -- it's now "yii"! So if you get ambitious and download the sample applications, don't go searching for yiic, because you won't find it. ;) I'm excited about the advanced application and the init scripts to toggle configurations, but I'm getting ahead of myself here ...
Part 2 should make its appearance this weekend as I will dive into transitioning an old Yii 1.1 application into Yii 2.0