It's been close to a decade since I did anything in PHP (PHP5), but since I know PHP5 had public (and private,and protected) accessors back then, but didn't have any real typing of parameters if I remember, I assume this is a design pattern to enforce typing on the object parameters. Also, a good amount of them have some other guard that throws an exception on specific problems. I think it's a valid design choice to decide that since some object variables may need special handling that is accomplished through accessor methods, just create them specifically for each item that needs public access, and while you're at it throw in a few sanity checks. That provides a consistent interface, where accessors are both named and act in the same manner (i.e. you don't have mixed method call and direct assignment).