Most of the recently hyped web applications are written in PHP, for example Facebook. Wasn't there a list recently with the 10 most successful startups (by whatever criterion), and 7 out of 10 were based on PHP?

That's not because PHP is especially great, today, but because there weren't any decent alternatives in 2004.

Rails is three-and-a-half years old, as a public project. The alternative frameworks are about the same age. There are programmers with ten years of PHP experience; there is nobody on Earth with so much as three years of Django experience. Give the newbs some time to settle in before you declare PHP's long-term victory. PHP has had a long headstart.

To have a successful startup that makes a 2007 list, you have to start learning programming before 2007. Back in 2003, PHP was pretty much the name of the game, unless you enjoyed being married to Microsoft or wanted to construct vast mountains of overdesigned, stateful, undeployable Java middleware. Or unless you were writing your own framework from scratch in an alternative language, like DHH, or the Django folks, or the Redditers.