How to return data from a callback function? (form validation)

[eluser]stormbytes[/eluser]
Pretty straight-forward question here:

I'm trying to return an array from a callback function. How would I do that?

I tried saving the array as flashdata, but for some reason it gets purged when the next model is called (in the same stack). I thought flashdata is preserved until the following http-request (page)?

Well anyhow, if there's a way to simply pass the array from the callback to 'somewhere', that would make things simpler altogether.

Cheers!