I've been tied to several procedural applications written in PHP over the past 10 years. Two of these are going away soon, and I need to get up to speed with OOP techniques. 

Are there good tutorials or books written for people who are skilled procedural coders? By skilled, I use functions heavily, and classify functions via different include files. I like clean, easy to follow code (and document accordingly). My brain has been trained to think procedurally, though experience taught me to break down code into re-usable parts (easier to maintain and update). I understand OOP is based around the same idea, but I need some help overcoming the hurdle of learning this new (to me) technique.