In a quick note from Dynamically Typed, there's a mention of the online publication of Paul Hudson's book Practical PHP Programming.

Harry's comments: Generally looks pretty good from what I've read and nice that goes from the absolute basics all the way to writing extensions. Would be great if Paul provided some kind of feedback mechanism, given he's gone online with it; there's various pieces of insight that could be added such as the page on included. Definately a good place to point people who are starting PHP from scratch.

While I haven't personally read this book myself, I can agree with Harry on the beginner's nature of the book. It starts with a history of PHP, moves through variables/arrays/objects, and goes all the way up to more difficult things (such as XML/XSLT, the graphics functionality, and working with sockets/mail).