voku / Arrayy

     * @psalm-return static<TKey,T>

     * @psalm-mutation-free

     */

    public function appendToEachKey($prefix): self

    {

        // init

        $result = [];

        foreach ($this->getGenerator() as $key => $item) {

            if ($item instanceof self) {

                $result[$prefix . $key] = $item->appendToEachKey($prefix);

            } elseif (\is_array($item)) {

                $result[$prefix . $key] = self::create($item, $this->iteratorClass, false)

                    ->appendToEachKey($prefix)

                    ->toArray();

            } else {

                $result[$prefix . $key] = $item;

            }

        }

        return self::create($result, $this->iteratorClass, false);

    }

    /**

     * Add a prefix to each value.

     * @psalm-return static<TKey,T>

     * @psalm-mutation-free

     */

    public function prependToEachKey($suffix): self

    {

        // init

        $result = [];

        foreach ($this->getGenerator() as $key => $item) {

            if ($item instanceof self) {

                $result[$key] = $item->prependToEachKey($suffix);

            } elseif (\is_array($item)) {

                $result[$key] = self::create(

                    $item,

                    $this->iteratorClass,

                    false

                )->prependToEachKey($suffix)

                    ->toArray();

            } else {

                $result[$key . $suffix] = $item;

            }

        }