function getKeysForDuplicates(array $array)
    {
        $duplicates = $newArray = [];

        foreach ($array as $key => $value) {

            if ( ! isset($newArray[ $value ])) {
                $newArray[ $value ] = $key;
                continue;
            }

            if (isset($duplicates[ $value ])) {
                $duplicates[ $value ][] = $key;
            } else {
                $duplicates[ $value ] = [
                    $newArray[ $value ],
                    $key
                ];
            }
        }

        return $duplicates;
    }