Well my first question would be, do you really need to extend p101? It looks to me like they're two completely different beasts, ie, p101() intializes your classes and adds objects to a library, whereas clean() is meant for sanitizing strings/variables. When you extend a class in Object Oriented Programming it's generally so that the child class can use some method or property of the parent/super class in conjunction with new methods that it defines. If the two classes don't use any similar properties or methods, and in this case, don't even really do the same thing, there shouldn't be a need to create the child->parent relationship of an extended class.

Um, and I don't want to insult your intelligence because I'm sure you can keep up, but broken down for a three year old, I guess I would say something along the lines of.... well, spyke, that's a question you should be asking your mom.
-m