It’s been a very long time since PHP-Calendar has seen any significant changes. A few years ago I started a project to improve both the UI and the code design. It never got to the point where it was releasable. Last year, I improved on this a bit and started using Symfony. You can see the progress on the v3.0 branch on GitHub.
I think one of the biggest improvements is moving from my weird custom form library to Twig templates. I hope to make things easier to read, understand, and contribute to. You’ll need to let me know how I do.
The demo calendars are currently broken due to moving to the site to GitHub. I’ll re-install them in a new location soon. There’s an open issue for this.