Google\Spreadsheet\DefaultServiceRequest::initRequest PHP Method

    protected function initRequest($url, $requestHeaders = array())
    {
        if (substr($url, 0, 4) !== "http") {
            $url = $this->serviceUrl . $url;
        }
        $ch = curl_init();
        curl_setopt_array($ch, $this->curlParams);
        curl_setopt($ch, CURLOPT_URL, $url);
        $headers = array();
        if (count($this->getHeaders()) > 0) {
            foreach ($this->getHeaders() as $k => $v) {
                $headers[] = "{$k}: {$v}";
            }
        }
        $headers[] = "Authorization: " . $this->tokenType . " " . $this->accessToken;
        $headers = array_merge($headers, $requestHeaders);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
        curl_setopt($ch, CURLOPT_USERAGENT, $this->getUserAgent());
        return $ch;
    }

 /**
  * {@inheritdoc}
  */
 protected function initRequest($url, $requestHeaders = [])
 {
     $this->accessToken = $this->refreshExpiredToken();
     return parent::initRequest($url, $requestHeaders);
 }