> Pretty much every PHP app in the world shares a database. So you've shifted your scaling problems from an area that programmers understand and control to a 1-MLOC mystery.

True, however in my experience it's pretty easy to scale the database layer. One beefy DB server can easily handle 2 or 3 front end servers with even mild caching. If you get aggressive in the caching strategy, one DB server can handle up to 10 front end boxes. And if you need to scale beyond that, replication is a well understood paradigm (sure, not by normal app developers, but there's plenty of resources out there).

> I bring this up because I have a few friends who make their living saving the asses of PHP programmers who buy the notion that PHP is magically easy to scale.

I never said that it was magically able to scale. I said that the language is easy to scale. What you do with it is on you. So if you're writing garbage code, you're going to get garbage scalability...