protected function _getCurlInitialization($url)
  {
    $connection = $this->_curl_init($url);

    $this->_curl_setopt($connection, CURLOPT_RETURNTRANSFER, 1);
    $this->_curl_setopt($connection, CURLOPT_FOLLOWLOCATION, 0);
    $this->_curl_setopt($connection, CURLOPT_HEADER, 1);
    $this->_curl_setopt($connection, CURLOPT_SSL_VERIFYPEER, 1);
    $this->_curl_setopt($connection, CURLOPT_SSL_VERIFYHOST, 2);
    $this->_curl_setopt($connection, CURLOPT_CAINFO, __DIR__ . '/cacert.pem');
    $this->_curl_setopt(
      $connection, CURLOPT_USERAGENT,
      'codebird-php/' . $this->getVersion() . ' +https://github.com/jublonet/codebird-php'
    );

    if ($this->_hasProxy()) {
      $this->_curl_setopt($connection, CURLOPT_PROXYTYPE, $this->_getProxyType());
      $this->_curl_setopt($connection, CURLOPT_PROXY, $this->_getProxyHost());
      $this->_curl_setopt($connection, CURLOPT_PROXYPORT, $this->_getProxyPort());

      if ($this->_getProxyAuthentication()) {
        $this->_curl_setopt($connection, CURLOPT_PROXYAUTH, CURLAUTH_BASIC);
        $this->_curl_setopt($connection, CURLOPT_PROXYUSERPWD, $this->_getProxyAuthentication());
      }
    }

    return $connection;
  }