public function current(): array
    {
        if (($headers = &$this->cacheKey(__FUNCTION__)) !== null) {
            return $headers; // Cached this already.
        }
        $headers = []; // Initialize.

        foreach ($_SERVER as $_header => $_value) {
            if (mb_stripos($_header, 'HTTP_') === 0) {
                $_header                          = preg_replace('/^HTTP_/ui', '', $_header);
                $_header                          = str_replace('_', '-', $_header);
                $headers[mb_strtolower($_header)] = $_value;
            }
        } // unset($_header, $_value); // Housekeeping.

        return $headers;
    }