code: protected function checkDataParam()
      {
          $branchNo = $this->branchNo;
          $merchantNo = $this->merchantNo;
  
          if (empty($branchNo) || mb_strlen($branchNo) !== 4) {
              throw new PayException('商户分行号，4位数字');
          }
  
          if (empty($merchantNo) || mb_strlen($merchantNo) !== 6) {
              throw new PayException('商户号，6位数字');
          }
      }
docs: 检查基本数据