As you might know, the "__autoload()" function, when used in a clever way, can eliminate almost completely the need to use the "require()/require_once()" and "include()/include_once()". [...] Now is the perfect time to move forward and start learning how to put the "__autoload()" magic function to work for you, and load your classes without having to include them manually into your PHP 5 object-oriented applications.

They show the more traditional approach with a code example (just using the require/include method) then show the difference in using a custom defined autoload function to tell the script where to find the libraries.