I've been using CodeIgniter for a few months and I keep finding the need to install 3rd party libraries that make it function more like Rails, specifically in its templates, testing, ORM, and before filters in controllers.
Is there a PHP MVC framework that more closely follows Rails conventions?
CakePHP started as a Rails clone, I believe, but has evolved to take advantage of PHP's language features (since Rails was written to do the same with Ruby, after all).
From all the frameworks I've tried (and I've tried many), Akelos PHP Framework is without a doubt, the one that best resembles Ruby on Rails (beware: I've only tasted RoR, I'm not an active developer):
Being a Ruby on Rails port to PHP, Akelos is also designed to make developers lives simpler by resolving complex problems with unusual speed and productivity.
In my opinion Akelos must be one of the best open-source PHP frameworks out there.
Id say CakePHP is pretty close - although i myself prefer Symfony. Symfony Rails-like in that it has all the different generators your probably used to. However, it allows a much eaiser path for customization than Cake and a lot of other similar php frameworks while being more robust out-of-the-box than the lighter frameworks like CI.