Here's an answer from the developers:
TideKit includes Zend as part of our PHP but we don't encourage full
blown PHP app development since this can limit capabilities and
platforms for deployment. Therefore, we've not looked at frameworks
like Symphony, CodeIgniter, and others to ensure they can be used.
Foremost, TideKit is a JS Platform that enables you to consistently
write your code once in a single language. With more than 100,000
packages of functionality available in JavaScript, there is not much
you cannot find these days (as opposed to write yourself). Together
with our native capabilities, TideKit is suitable for virtually
anything you can imagine for HTML5, hybrid, or native apps.
We are currently working on our demos to provide a glimpse of
TideKit's capabilities. TideKit is very flexible to work with and
we'll be demonstrating app work flows that mean fast and enjoyable
development.
Source: https://blog.tidekit.com/post/from-a-desktop-perspective-tidekit-for-tidesdk-developers#comment-1568824440
As I have seen, it's a quite neat tool to have, but the PHP version is not the latest one (also webkit is pretty dated in it), so functions might not work exactly as they should. A major issue what I came accross when using Tide is that it does not treat directories pretty well. I had to set a lot of working directories inside the scripts (also with ifs so it would always point to the right directory) - it doesn't seem to like relative paths that much.
Anyway, I think it's a great tool, yes, it supports PHP, but if you were to use a framework with it, you probably would lose all your hair. If you plan to just write a light app in PHP on your own, that's perfectly fine then, but you still have to troubleshoot some due to the directory issue mentioned above.
Hope this helps.