i wouldn't say that.
most of my fello programmers haven't learnt programming languages by reading books. They all learnt it while playing with the codes. You couldn't learn programming with just a book.
A book can help of course if you want to look up some functions for example, but php.net is a good ressource for that, too.

'or some form of educating'

So reading the code can also come from that, ie. self education. However I do agree with you to a certain extent, I from time to time read PHP and try to understand it, it's a great way (and quite fast) to learn a lot of new things in PHP.