As you can see, one is using <type>callback</type> the other <type>mixed</type>, the reasons being obvious - a callback is just a string or an array... so the question here is, do we respect the callback type as its own which consists of 'mixed' data, or do we use mixed? I personally feel that callback is more descriptive. as I am going through all callback functions anyways, I will change them all to have the same, whatever is decided. I'm not entirely bothered which is chosen, so long as one is, and its stuck too.
I am fine with the callback type, and the "handler" name to use for callback paramater names.
Goba