code: private static function build($data)
      {
          if (!is_array($data)) {
              return $data;
          }
          foreach ($data as $key => $value) {
              if (is_string($value) && class_exists('CURLFile', false) && stripos($value, '@') === 0) {
                  $filename = realpath(trim($value, '@'));
                  if ($filename && file_exists($filename)) {
                      $data[$key] = new \CURLFile($filename);
                  }
              }
          }
          return $data;
      }
docs: POST数据过滤处理
  @param array $data
  @return array