Padraic Brady has posted about the art of deception that several publishers have involved themselves in - already publishing books about PHP6.
I was strolling around a bookstore today, Easons on O'Connell Street here in Dublin, when I found myself staring at a bookshelf in near shock. Kid, I thought, you've been out of the loop for only two months and somehow those crazy people have managed to release PHP 6 right under your nose! [...] The more I stared at the three youthful faces grinning at me from the cover, the more I convinced myself this was a publishing error. No way was PHP6 going to be released without me noticing. Google Reader would have been on fire with that news. So what the hell was I looking at? I was apparently looking at a big fat lie.
He goes on to talk about PHP6 (aka the "long standing grail" of PHP) and how publishers, apparently misinformed as to the release date of the version, preempted its release and assumed that it would be out as soon as or before the book was. Obviously this was the wrong choice and now they're paying for it with the egg on their face.
Sure these PHP6 books have a lot of the PHP 5.3 features mentioned in them, but they're mashed up with other features that won't be ready until PHP6 actually arrives. Oddly enough, upon looking at the contents of most of the books, Padraic discovered something interesting - their content is less about PHP6 and more about the PHP 5.2 series that was current. Seems they're only really PHP6 in name.