public function getHeader($header)
    {
        if (array_key_exists($header, $this->responseHeaders)) {
            return $this->responseHeaders[$header];
        }
        // Do case-insensitive search
        foreach ($this->responseHeaders as $k => $v) {
            if (strtolower($k) == strtolower($header)) {
                return $v;
            }
        }
    }