Programming languages for large web applications?

dominion writes: "After building a huge open source web application, I've started to intimately learn about the shortcomings and downfalls of building a large PHP application. I haven't even yet hit 1.0, but I'm considering the possibility that I might need to move over to another development platform for later versions. Later versions should be heavily AJAX oriented, so I've considered a rewrite using Ruby on Rails or Java for the server side. Google's Web Toolkit looks interesting, and makes Java look like a competitor. Here's the problem, though: The project (Appleseed) is distributed social networking software, which means that the more sites that are out there that run it, the more successful it is. I originally chose PHP because so many webhosts allow users to run PHP scripts, and moving to Ruby on Rails or Java makes it much harder for just about anybody to set up a node. Is it worth it, then, to pull my hair out over PHP's quirks? PHP6 seems to make the language a bit more tolerable, but with the amount of webhosts who still run PHP4, wouldn't making a move to PHP6 defeat the purpose of sticking with PHP in the first place?"