Removing Items from an Array

Hi all, I'm really struggling here! I have a large, multi-dimensional array that I want to "clean-up" a bit before committing to a database. I want to remove quite a bit of the array but using the KEYs not the values. I know the keys I want to keep and I know the keys I want to get rid of. I want to keep the structure and sequence of the array in tact. All of the array traversing functions in PHP seem to either: only work on the values, or do not allow the removal of elements of the array! Can anyone offer a clue bat to a tired old array walker! Thanks Alan