Advice on appropriate datastructure

Question

Hi everyone, I've got a bunch of related tables I'm retreiving data from, and end result is I end up with a bunch of (key,value) pairs for an object. So one object might have: total, 10 tax1, 2 and another object might have these values: total, 20 tax1, 4 tax2, 3 In the end, I want to sum up all the common fields in my returned objects so I've got something like: total, 30 tax1, 6 tax2, 3 And I want to display this final info in a form. The question is, what is the best datastructure to store everything in? I thought of a 2-dimensional array, but then I end up going through a lot of loops to add everything up later (checking key fields, adding up value fields if equal, etc). Then I thought maybe an extended hashtable class with the add() method overridden, but I'm not sure how to do that. Any suggestions?