php 5.6+ 微信上传媒体文件报错解决方案

php在5.6以后修改了上传文件的方法
以下是上传图片示例

    public function upload_media_test($file,$access_token){
            $url="http://file.api.weixin.qq.com/cgi-bin/media/upload?access_token={$access_token}&type=image";
            $file_data['media']=new CURLFile(realpath($file));
            $result=json_decode(uploadMedia($url,$file_data),1);
            var_dump($result);
        }
        function uploadMedia($url,$fields){
            $ch = curl_init($url) ;
            curl_setopt ($ch, CURLOPT_SAFE_UPLOAD, false);
            curl_setopt($ch, CURLOPT_POST, 1);
            curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
            curl_setopt($ch, CURLOPT_POST, 1);
            curl_setopt($ch, CURLOPT_POSTFIELDS,$fields);
            curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
            $result = curl_exec($ch) ;
            if (curl_errno($ch)) {
                return curl_error($ch);
            }
            curl_close($ch);
            return $result;
        }