Pinq\Iterators\Standard\FlatteningIterator::doFetch PHP Метод

    protected function doFetch()
    {
        while (($innerElement = $this->innerIterator->fetch()) === null) {
            if (($outerElement = $this->outerIterator->fetch()) === null) {
                return null;
            }
            $outerValue = IteratorScheme::adapter($outerElement[1]);
            $this->innerIterator = $outerValue;
            $this->innerIterator->rewind();
        }
        return [$this->count++, &$innerElement[1]];
    }