ArrayObject - Posibillity to add key => value pair per default?

Hey, I've just discovered the ArrayObject class, but it seems to not be well documented, so here is my problem: You can use ArrayObject::append() to add a new value to the array, but is there also a method to add a new key and value? And I know that I could extend the class and write my own method but isn't this quite a base method for arrays in php? So maybe I just missed a obvious point? Quick example: Without ArrayObject: 1. $array[] = $value 2. $array[$key] = $value With ArrayObject: 1. $arrayObject->append($value) 2. ??? -eddy