PHP使用curl请求实现post方式上传图片文件功能示例

在调用第三方api接口时，有时会遇到通过http协议上传图片，以下是一个微信公众平台新增永久素材的例子(使用前请阅读相关微信文档)；
php代码：

/* 使用curl函数 */
$url = "https://api.weixin.qq.com/cgi-bin/material/add_material?access_token=ACCESS_TOKEN&type=image";
$post_data = array(
  'media' => '@bag03.jpg',
);
$response = curl_http($url, 'POST', $post_data);
$params = array();
$params = json_decode($response,true);
if (isset($params['errcode']))
{
  echo "error:" . $params['errcode'];
  echo "msg :" . $params['errmsg'];
  exit;
}
var_dump( $params );
/**
 * http请求方式: 默认GET
 */
function curl_http($url, $method="GET", $postfields){
  $ch = curl_init();
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
  curl_setopt($ch, CURLOPT_URL, $url);
  switch ($method) {
    case "POST":
      curl_setopt($ch, CURLOPT_POST, true);
      if (!empty($postfields)) {
        $hadFile = false;
        if (is_array($postfields) && isset($postfields['media'])) {
          /* 支持文件上传 */
          if (class_exists('\CURLFile')) {
            curl_setopt($ch, CURLOPT_SAFE_UPLOAD, true);
            foreach ($postfields as $key => $value) {
              if (isPostHasFile($value)) {
                $postfields[$key] = new \CURLFile(realpath(ltrim($value, '@')));
                $hadFile = true;
              }
            }
          } elseif (defined('CURLOPT_SAFE_UPLOAD')) {
            if (isPostHasFile($value)) {
              curl_setopt($ch, CURLOPT_SAFE_UPLOAD, false);
              $hadFile = true;
            }
          }
        }
        $tmpdatastr = (!$hadFile && is_array($postfields)) ? http_build_query($postfields) : $postfields;
        curl_setopt($ch, CURLOPT_POSTFIELDS, $tmpdatastr);
      }
      break;
    default:
      curl_setopt($ch, CURLOPT_CUSTOMREQUEST, $method); /* //设置请求方式 */
      break;
  }
  $ssl = preg_match('/^https:\/\//i',$url) ? TRUE : FALSE;
  curl_setopt($ch, CURLOPT_URL, $url);
  if($ssl){
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE); // https请求 不验证证书和hosts
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE); // 不从证书中检查SSL加密算法是否存在
  }
  $response = curl_exec($ch);
  curl_close($ch);
  if(empty($response)){
    exit("错误请求");
  }
  return $response;
}
function isPostHasFile($value)
{
  if (is_string($value) && strpos($value, '@') === 0 && is_file(realpath(ltrim($value, '@')))) {
    return true;
  }
  return false;
}