In response to this post on the ActsAsFlinn blog's comments on ActiveRecord in PHP, Arnold Daniels has some comments of his own on the subject - specifically about the need for more work on the object oriented side of things in PHP natively.
Today I read an article about how Active Record is implemented in Ruby. In this article he lays down how things are done in Ruby and how that is not possible on PHP. Though I agree with him on a large part, there are a few site notes to make here.
Arnold talks about a solution to an issue mentioned in the ActsAsFlinn blog - the addition of methods to a preexisting class - via the runkit extension. He gives a PHP translation of the Ruby code from the other post and includes a few proof of concepts to show it in action. You can download the code if you'd like to try it out yourself.