modifying within foreach

In the following example: foreach ($results as $key => $item) { //bla bla bla -- unset some of the $items } I want to modify $results within the foreach. In other words, during a given pass of this iteration, I want to delete some of the items based on particular conditions. Then on the next pass thru the foreach, I want $results to be the newer, modified array. This does not seem to work. It appears that the foreach statement is implemented such that $results is read into memory at the start so that any modifications I make to it during a given pass, are ignored on the next pass. Is this true? If so, is there a way that I can tell the foreach statement to re-read the array $results? Or am I just going against the grain here? -Andres