The problem is the source for that "everyone" [is still using PHP4] claim. The most widely referenced stats are the Nexen stats, and according to them 70%+ of the world still uses PHP 4. Horrors!
He takes a closer look at the stats and comes up with a slightly different sort of conclusion that the stats can't really measure. They can show the server-based usage measurements of PHP4 vs PHP5, but they can't show the number of developers behind each of them.
According to Larry:
Even if we assume that 70% of PHP developers are using 70% of random servers running PHP, and that they're all using proprietary, one-off applications on a server with a sysadmin who refuses to upgrade at a company that has no support contract with any distribution vendor... Where are they?