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.