this can have side effects:

- some iterators can be iterated only once (``NoRewindIterator`` and generators for instance, or PDOStatement according to a recent discussion in the Twig mailing list)
- some iterators are lazy, and will be initialized
- if you build an infinite iterator (expecting to wrap it in a LimitIterator later or to break the loop explicitly), calling ``iterator_to_array`` on it will be an infinite loop. the SPL even has an [``InfiniteIterator`` class](http://php.net/InfiniteIterator) looping over an iterator forever