If you try these strings on a URL that isn't PHP, they won't work, even if the web server has PHP support. In any case you can:
1. Try it somewhere.
2. Visit http://37signals.com/index.php
3. Ask'em directly.
This is the most asinine thing I've ever read on here. The first thing any smart person can figure out is that RoR doesn't make 37signals what they are. They have always said that themselves. Fast agile development, and all the other things they talk about in their Getting Real book make them what they are, but certainly not which language/framework. This is a lot like debating what care you're going to buy based on what the manufacturer of the car that won NASCAR last weekend was.
Really? The most asinine thing ever? I don't agree with that, but you do have a point. Still, it is interesting that 37Singnals is using PHP, not shocking, not mind-blowing, but interesting. Just like it would be interesting if Microsoft were using Java for MSN.
Given that Flickr is written in PHP, Delicious in Perl, Reddit in Python, Foo in Bar, I think that unless you are using something like Java or C++ that really will make you 5 times slower in the development process it does not really matter too much. IMHO this is highly related to the nature of web applications where the design of the UI, the feeling, and the idea you are developing is much more important than complex data structures and funky algorithms (being the only real challenge scalability in many projects).
What's nice is that actually if you master computer science it counts even in web programming as long as there are non trivial problems to solve, but this happens 5% of the times compared of 95% when you write, for example, a compiler.
http://basecamphq.com/?=PHPB8B5F2A0-3C92-11d3-A3A9-4C7B08C10000 http://backpackit.com/?=PHPB8B5F2A0-3C92-11d3-A3A9-4C7B08C10000