Clone FilterIterator/IteratorIterator?

Hi, I want to use an Iterator that returns an the inner iterator, with an additional FilterIterator applied. The returned iterator should be separated from my inner iterator, to avoid errors like 'ArrayIterator::next(): Array was modified outside'. To avoid this, I think it might be the best to simply clone the inner iterator. Unfortunatly, if the innerIterator is an FilterIterator, so cloning will throw an exception: PHP Fatal error: Call to undefined method ArrayIterator::getIterator() Is there a good reason why i can't clone a FilterIterator? Testcase: <?php class MyIterator extends FilterIterator { public function accept() { return true; } } $arr = new ArrayObject(array()); $it1 = new MyIterator($arr->getIterator()); $it2 = $it1->getIterator();