public function getHeaderValue($headerName)
    {
        if (is_string($headerName) && count($this->headers) > 0) {
            $lowCaseHeaders = array_change_key_case($this->headers, CASE_LOWER);
            $lowCaseHeaderName = strtolower($headerName);
            if (isset($lowCaseHeaders[$lowCaseHeaderName])) {
                return $lowCaseHeaders[$lowCaseHeaderName];
            }
        }
        return false;
    }