Dave Marshall has posted some of the notes he made when he ported an application from a language he didn't know (very well), Ruby, into PHP.
I'm porting from a language I'm not familiar with, and I'm porting code that I don't necessarily understand! I've written a couple of rails apps, but they were very basic, and I have no real clue with the delicacies of the ruby language.
He talks about the project - a migration tool - and how he had to work through things like the current file structure, converting functionality like exceptions and getting over Ruby's singleton use. He also shows how he could replicate some of the Ruby functionality with closures and how he set it all up to use Zend_Tool as the application structure.