Dotclear 2 was, until now, not compatible with the latest version of PHP, numbered 5.3 and released this summer. Although most of the work was done, we decided not to include it in Dotclear 2.1.6, as it needed a review of pretty much all the code and it would have been too big a chance to break something for the users.
So we released the 2.16, then switched development to the 2.2 branch, where we included all the necessary PHP 5.3 patches. That's this version you will find in our nightly builds. It is of course, as far as we know, compatible not only with PHP's last version but also with the preceding ones.
Several other changes were implemented, none of them should trigger a bigger reaction than a It wasn't quite like that last time...
With one notable exception:
We redesigned the internal settings system: whereas we already used namespaces for it, they were used for setting the value but not for retrieving them. The new design deals with that shortcoming: you'll have to use $settings->namespace->value rather than $settings->value. The old system is still supported, but as it is deprecated, it will raise a notice. Do not forget to deactivate PHP notices in anything close to a production environment (well, you should anyway.)
So go grab it, test it, use it, abuse it, and feel free to ask any question on the forum.