php版本区别：

    1. <=5.4 curl上传文件只支持@语法
    3. = 5.5 支持@语法和CURLFile类
    5. 大于=5.6 只支持CURLFile类

    // 兼容性写法参考示例

    1. $curl = curl_init();
    3. if (class_exists('\CURLFile')) {// 这里用特性检测判断php版本
    4.      curl_setopt($curl, CURLOPT_SAFE_UPLOAD, true);
    5.         $data = array('file' => new \CURLFile(realpath($source)));//>=5.5
    6.  } else {
    7.      if (defined('CURLOPT_SAFE_UPLOAD')) {
    8.          curl_setopt($curl, CURLOPT_SAFE_UPLOAD, false);
    9.      }
    10.      $data = array('file' => '@' . realpath($source));//<=5.5
    11.  }
    13.  curl_setopt($curl, CURLOPT_URL, $url);
    14.  curl_setopt($curl, CURLOPT_POST, 1 );
    15.  curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
    16.  curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
    17.  curl_setopt($curl, CURLOPT_USERAGENT,"TEST");
    18.  $result = curl_exec($curl);
    19.  $error = curl_error($curl);