Rad wrote on Jun 19^th, 2008 at 8:11pm:

Sure, but internally to the PHP system a $ outside a string and a $ inside one have to be treated by different code; the situations deliberately look similar so that there are less things to learn, but the language has to work quite hard to maintain that illusion.

Internally to the language, what it does in order to make this magic happen can have odd consequences. This makes it hard to intuitively know what the fastest of all the dozens of equivalent ways of doing the same thing are, but because almost everything does work it's much easier to write something and have it be useful.