Why not just do this instead?

iterator_to_array(new RecursiveIteratorIterator($it));

Ignore my previous comment. That would flatten the array instead. My apologies.

I currently have this... which also isn't restricted to just \RecursiveIterator(s) but uses a more generic approach.

<?php
function recursive_iterator_to_array(\Traversable $it)
{
    $result = array();
    foreach($result as $key => $value) {
        if($value instanceof \Traversable) {
            $result[$key] = recursive_iterator_to_array($value);
        } else {
            $result[$key] = $value;
        }
    }
    return $result;
}

TO: franssen dot roland

In your code is error. On line 5 it should be "foreach($it as $key => $value) {"