PHP5 Object Oriented Programming
Object Oriented Programming can easily confuse even the best developers. There is a lot of power behind being able to debug an application when you know exactly what will be executed next. However, when working with objects, you will find that you can accomplish a whole lot more than what you realized was available in PHP.
Documentation
We all know PHP, we all have worked with classes and objects in php. While these are not new concepts for us, I've found that the help sections on php.net for classes and objects taught me a few things I was never aware of. There is also the Standard PHP Library, which allows for special functionality that PHP never used to support(like having an object that behaves as an array), these libraries create a massive new potential for PHP, which is only available when using object oriented programming