运费单商品计算，购物车需要多商品计算

//type=1是按照件数
if($template['type'] == 1){
            //          echo '按数量计算,商品数量'.$number.'<br>';
            //          echo $items['first'].'件内'.$items['amount'].'元，每多'.$items['add'].'件，增加'.$items['add_amount'].'元<br>';
                      if($number <= $items['first']){
            //            echo '小于首数量<br>';
                        $amount = $items['amount'];
                      } else {
            //            echo '首件费用：'.$items['amount'].';续费：'.$items['add_amount'].'续件：'.$step.';<br>';
                        $step = ceil(($number - $items['first'])/$items['add']);
                        $amount = $items['amount']+$step*$items['add_amount'];
                      }
                    } else {
            //          echo '按重量计算,商品重量：'.$weight.'<br>';
                      //按重量
                      if($weight <= $items['first']){
            //            echo '小于等于首重<br>';
                        $amount = $items['amount'];
                      } else {
            //            echo $items['first'].'g内'.$items['amount'].'元，每多'.$items['add'].'g，增加'.$items['add_amount'].'元<br>';
            //            echo '重量：'.$weight.'<br>';
                        $step = ceil(($weight - $items['first'])/$items['add']);
            //            echo '续重：'.$step.'<br>';
                        $amount = $items['amount']+$step*$items['add_amount'];
                      }
                    }
                 //这就是结果了加油
                 $amount;

等等，我封装以下哈

//$freightitems=["first"=>"首件或者首重","amount"=>"首件或者首重的费用","add"=>"续件或者续重","add_amount"=>"续件或者续重的费用","type"=>"1=按照件数"];

$freightitems=["first"=>"1","amount"=>"1","add"=>"1","add_amount"=>"1","type"=>"1"];
function freight($number,$a_weight, $freightitems){
          $amount=0;
          if($freightitems['type'] == 1){
            //          echo '按数量计算,商品数量'.$number.'<br>';
            //          echo $items['first'].'件内'.$items['amount'].'元，每多'.$items['add'].'件，增加'.$items['add_amount'].'元<br>';
                      if($number <= $freightitems['first']){
            //            echo '小于首数量<br>';
                        $amount = $freightitems['amount'];
                      } else {
            //            echo '首件费用：'.$items['amount'].';续费：'.$items['add_amount'].'续件：'.$step.';<br>';
                        $step = ceil(($number - $freightitems['first'])/$freightitems['add']);
                        $amount = $freightitems['amount']+$step*$freightitems['add_amount'];
                      }
                    } else {
            //          echo '按重量计算,商品重量：'.$weight.'<br>';
                      //按重量
                      if($weight <= $freightitems['first']){
            //            echo '小于等于首重<br>';
                        $amount = $freightitems['amount'];
                      } else {
            //            echo $items['first'].'g内'.$items['amount'].'元，每多'.$items['add'].'g，增加'.$items['add_amount'].'元<br>';
            //            echo '重量：'.$weight.'<br>';
                        $step = ceil(($weight - $freightitems['first'])/$freightitems['add']);
            //            echo '续重：'.$step.'<br>';
                        $amount = $freightitems['amount']+$step*$freightitems['add_amount'];
                      }
                    }
                 //这就是结果了加油
              return   $amount;
}