I'm relatively new to objects and design patterns and have been learning them for only the last 4 months. As most people know PHP 5 was the first iteration of a half way decent obeject implementation in PHP. Therefore there is just now beginning to be OO related design books on the market for this functionality. I've bought them all as my opinion is this on trumps the rest. It's not going to tell you much on object theory or PHP's object syntax. However when it comes to design architecture it's be best I've found for PHP specifically. Outside of that if you're looking for good Design Pattern and Architecture theory stuff you should start reading Java based books as there's some really good ones.