The very first programming book I bought was "PHP6 and MySQL5" by Larry Ullman. I bought that one specifically because I had another job (career, really) and I knew it was going to take a while before I really got into programming and I didn't want to buy a book that was going to be out of date in 2 years. That book is now 6 years old, out of date, and PHP6 is still not released. Maybe 6 is just an unlucky number with Perl unable to make that goal as well, but either way I'm not holding my breath.
I've since moved on to more well thought out languages, though PHP keeps pulling me back in. I'm currently having to support a CI app that hasn't had a line of code added to it since 2008, and the only thing I can say, even though I appreciate the language and how far it's pushed the web, I'm glad it's no longer my go-to language of choice. Keep PHP5 around for a while so apps like this one can continue on, but PHP6 is _LONG_ overdue.