PHP vs. Rails on Squidoo

This might be better titled as Frameworks vs. Languages. Of course, since most people writing modular code will end up making a framework for their application, it's really Shelf Frameworks vs. In-House Frameworks.

Of course, there's also a third option, niche open source frameworks (every PHP developer and their dog has a PHP framework, and not all of them suck). Chances are, if you look hard enough, you'll be able to find an OSS framework in the language you need that would be fairly similar to one you'd make yourself. If the code is well designed, you can simply cut out what you don't need and add what you do.