private function rankAcceptCharsetHeaders(array $charsetHeaders): array
    {
        usort($charsetHeaders, [$this, 'compareAcceptCharsetHeaders']);
        $rankedCharsetHeaders = array_filter($charsetHeaders, [$this, 'filterZeroScores']);

        // Have to return the values because the keys aren't updated in array_filter()
        return array_values($rankedCharsetHeaders);
    }