public function next()
{
$this->initializeChunkIterator();
$this->position++;
$this->chunkIterator->next();
if (!$this->chunkIterator->valid()) {
$this->iterator->next();
if ($this->iterator->valid()) {
$current = $this->iterator->current();
$this->chunkIterator = new ArrayIterator($current);
}
}
}