php - 在 PHP 中，当订购多个商品时，如何将这些商品的数量减 1？

Question

这是我使用过的代码；问题只是 1 件 数量可以一次递减；多个商品数量不能 递减。

 <?php


    $dbhost = "localhost"; 
    $dbuser = "root";
    $dbpass = "";
    $dbdb = "yumyum";


    $connect = mysql_connect($dbhost, $dbuser, $dbpass) or die("connection error");


    mysql_select_db($dbdb) or die("database selection error");


    $id = $_POST['id'];


    $query1=mysql_query("SELECT Quantity,id FROM `yumyum`.`food` where  `food`.`id` LIKE $id");
    $rows = array();

    while($r = mysql_fetch_assoc($query1)) {

        $output = $r['Quantity'];


            echo $output;
            $query2=mysql_query("UPDATE food SET Quantity = Quantity - 1 where  `food`.`id` LIKE ".$r["id"]);
    }

    ?>

Answer 1

你能试试这个吗

$query2 = mysql_query("UPDATE food SET Quantity = Quantity - 1 where  `food`.`id` = '".$r["id"]."' ");

或者

        $query1=mysql_query("SELECT Quantity,id FROM `yumyum`.`food` where  `food`.`id` = '".$r["id"]."' ");
        $rows = array();

        while($r = mysql_fetch_assoc($query1)) {

             $output = $r['Quantity'];      

             $output = $output-1;
             $query2=mysql_query("UPDATE food SET Quantity = '".$output."' where  `food`.`id` = '".$r["id"]."' ");
        }