AppendIterator example

if (1 === \count($this->dirs) && 0 === \count($this->iterators)) {
            $iterator = $this->searchInDirectory($this->dirs[0]);

            if ($this->sort || $this->reverseSorting) {
                $iterator = (new Iterator\SortableIterator($iterator, $this->sort, $this->reverseSorting))->getIterator();
            }

            return $iterator;
        }

        $iterator = new \AppendIterator();
        foreach ($this->dirs as $dir) {
            $iterator->append(new \IteratorIterator(new LazyIterator(fn () => $this->searchInDirectory($dir))));
        }

        foreach ($this->iterators as $it) {
            $iterator->append($it);
        }

        if ($this->sort || $this->reverseSorting) {
            $iterator = (new Iterator\SortableIterator($iterator, $this->sort, $this->reverseSorting))->getIterator();
        }