使用 chooseMessag 服务端未找到文件？

wx.chooseMessageFile({       count: 1,       type: 'file',       success(res) {         wx.uploadFile({           url: 'http://xxx',           filePath: res.tempFiles[0]['path'],           name: 'file',           success(res) {                        }         })       }     })

$tmp_file = $_FILES['file']['name'];         $file_types = explode(".", $tmp_file);         $file_type = $file_types [count($file_types) - 1];         $savePath = ROOT_PATH . 'public' . DS . 'uploads' . DS;         $str = date('Ymdhis');         $file_name = $str . "." . $file_type;         if (!copy($tmp_file, $savePath . $file_name)) {             return '上传失败';         }

使用的时候 报no such file or directory

请问是什么缘故