PHP Phrasebook
isbn: 0-672-32817-8
Not one to read cover to cover. Think of it like a cook book with much shoter recipies. This is allways with me. Need a quick function, its in there. A must for pocket reference lovers.

Pro PHP Security
isbn: 1-59059-508-4
A great book. It starts with having you examine the base you are running your scripts on. IE it is pointless to secure the hell out of a PHP script if you are running it on Windows me and 3 year old apache. It walks you from start to finish. Well finish as of today.

Ajax and PHP Building Responsive Web Applications
isbn: 1-904811-82-5
Not the best book. But if you suck in javascript like me, it will give you a good idea in AJAX development. I would not rely on thier code though. Tweek thier code.
My New site OpenEyes