public function getUserAgentHeader()
    {
        // If has own User-Agent
        $userAgentName = $this->getUserAgentName();
        if ($userAgentName) {
            return $userAgentName;
        }

        $userAgent = sprintf('%s/%s/%s (PHP/%s.%s.%s', $this->getLibraryName(), $this->getVersion(), $this->getPublicKey(), PHP_MAJOR_VERSION, PHP_MINOR_VERSION, PHP_RELEASE_VERSION);

        $framework = $this->getFramework();
        if ($framework) {
            $userAgent .= '; '.$framework;
        }

        $extension = $this->getExtension();
        if ($extension) {
            $userAgent .= '; '.$extension;
        }

        $userAgent .= ')';

        return $userAgent;
    }