我如何做 "buy 3 and pay 2" 数学？

Question

我有一个购物车，我需要构建报价功能，我已经完成了百分比折扣，我需要一些关于数量促销的帮助。

例如，如果客户购买 3 件商品，他只支付 2 件，但如果他想购买 5 件商品，我必须只为 3 件商品申请促销，其中 2 件是全价。

这是我的代码

    $quand_in_cart =  '5'; //quantity for product X in the cart
    $prod_price = '1.5'; //product price

    $percentage_off = NULL;
    $buy_any = 3; //promotion on 3 items
    $for_the_price = 2; //pay only 2

    if($percentage_off and $quand_in_cart >= $buy_any){

        $price_discount = ($percentage_off/100) * $quand_in_cart; //works percentage done.

    } elseif ($buy_any && $for_the_price) {
        if($quand_in_cart >= $buy_any){
            //here i need some help
        }
    }

Answer 1

用 Rest X 全价买 3 付 2。

在数学中它的意思是：

items_to_pay = floor(amount / 3) * 2 + X, with X = amount mod 3

因此在您的代码中：

$price = $prod_price * ((floor($quand_in_cart / $buy_any)*$for_the_price + ($quand_in_cart % $buy_any))

编辑：更多解释

floor($quand_in_cart / $buy_any)*$for_the_price // for every 3, only add 2 to the price
($quand_in_cart % $buy_any) // how many items are the rest if you devide by $buy_any

将这两个值相加，就得到了必须乘以一件商品价格的商品数量。就是这样。

我如何做 "buy 3 and pay 2" 数学？

How do I do "buy 3 and pay 2" math?

php

math

shopping-cart

percentage

e-commerce