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;
}