For a long time I experimented with PHP frameworks to see if I could capture the rails magic, but so much of it has nothing to do with the code/API itself (and more to do with the culture and community around the technologies). I'm now a full-time rails dev and hope that I will never have to use PHP again.

i do rails and php and frequently switching between the two made me write halfmoon (https://github.com/jcs/halfmoon). it's basically a tiny framework for php that has a syntax like rails (where php allows it - php 5.4's new short array syntax should clean things up quite a bit once it comes out). it uses an existing php port of activerecord (http://phpactiverecord.org) so all of the finders, associations, and validations work much the same.

as you can see by the code, it doesn't aspire to be a full port of rails, but it does routing, controllers, models, and views similarly enough. it's probably closest to the syntax of rails 2.2.

i use it in production for a handful of low-traffic sites (http://hntrades.com, http://4m.blandroid.org, http://domainical.org) and mostly hack on it when i'm working on a project and need a new feature or find a bug. it doesn't have any community or documentation outside of the README, but the project works well enough to keep me sane when i'm writing php.

I'm genuinely interested in your reason for not just using rails full-time. Is it because of the perceived deployment difficulty?

sometimes the project needs to use existing php libraries or code, sometimes it needs to be portable and php is easier to host and maintain, and sometimes i just don't want to deal with setting up and maintaining another rails site.