public static function delimit(array $array, string $prepend = '', string $delimiter = null)
    {
        // Results holder.
        $results = [];

        // Which string delimiter should we use?
        if (null === $delimiter) {
            $delimiter = static::$delimiter;
        }

        foreach ($array as $key => $value) {
            if (is_array($value) && !empty($value)) {
                $results = array_merge($results, static::delimit($value, $prepend.$key.$delimiter));
            } else {
                $results[$prepend.$key] = $value;
            }
        }

        return $results;
    }