As they say,
Core is a slow-moving branch that will be used as the base for EllisLab commercial products such as ExpressionEngine and MojoMotor. It will continue at a similar pace that CodeIgniter has in the past and will be useful for large commercial applications that require the upmost in stability and backward/forward compatibility at a pace more typical of SLA backed Enterprise products. Core is publicly available with tagged downloads at BitBucket.
Reactor is a community driven branch of CodeIgniter that will enable faster adoption of the best community submitted code to the framework. This means the community can create a fork of the project on BitBucket and contribute bug fixes, new features, documentation improvements, etc and have it reviewed by a code-review team called Reactor Engineers. These Engineers are primarily responsible for driving the development of the framework.
In simple words, Reactor will be managed by community + Ellislab and Core will be managed solely by Ellislab.
Some interesting things I liked,
- Support for PHP 4.x is gone
- Application Folder now sits outside System folder
- CLI support (I am still trying to figure it out)
- Full Query String support
- memcache and APC support
Also, Ellislab has changed the file structure a lot. Check out change log to know more.
In all, new version seems interesting. Though moving 1.7.x apps to 2.x is not easy. Since, Plugins have been deprecated, you will need to convert plugins either into libraries or helpers. Also, some of the libraries may not work with 2.x.
The only thing that is making me doubtful is why CI has been split up into 2 branches? Is Ellislab trying to make money by creating an Enterprise version? I hope they don’t.