使用PHP更新数组可以估算数据库中的现有库存水平和价格

当用户可以购买产品时，我正在创建一个网站 . 我已经创建了这个网站的管理员端，我正在尝试创建一个页面，其中管理员一旦登录，就可以更新myphpadmin数据库上某个产品的库存水平 . 到目前为止，我已设法将代码放到我的数据库中更新的阶段，而不是所选产品 . 相反，它会创建一个包含库存水平和价格的新记录 . 我使用以下命令从上一页获取了产品ID：

echo "<input type=hidden name=h_prodid value=".$stockid.">";

因此，当管理员点击更新链接时，他们会到达包含该特定产品的当前详细信息的页面 . 然后，他们输入一个或两个值来更新此特定产品，但是当前将新记录插入到数据库中，而不是更新现有的记录 . 请参阅下面的代码 .

<?php

session_start();

include("db.php");

//create a variable called $pagename which contains the actual name of the page
$pagename="Product Update Confirmation";

//call in the style sheet called ystylesheet.css to format the page as defined in the style sheet
echo "<link rel=stylesheet type=text/css href=mystylesheet.css>";

//display window title
echo "<title>".$pagename."</title>";
//include head layout 
include("adminheadlayout.html");

//display the name of the site and the date dynamically. See uk.php.net
echo date ('l d F Y H:i:s');
echo "<p></p>";

include ("detectlogin.php");

//display name of the page
echo "<h2>".$pagename."</h2>";

//Capture the details entered in the form using the $_POST superglobal variable
//Store these details into a set of new variables
$newprice=$_POST['p_priceupdate'];
$newquantity=$_POST['p_quantityupdate'];
$prodid=$_POST['h_prodid'];

//If any of the variables is empty
if (!$newprice and !$newquantity)
{
echo "<br>Please enter a value for price and/or quantity ";
echo "<br>Go back to <a href=editstock.php>Edit Stock details</a>";
}
else
{
if (!$newprice or !$newquantity)
{
    //insert a new record in the order table to generate a new order number. 
    //store the id of the user who is placing the order as well as the current date and time
    $productupdateSQL="insert into Products (prodPrice, proQuantity, prodId)
    values ('".$newprice."', '".$newquantity."', '".$prodid."')";
    $exeproductupdateSQL=mysql_query($productupdateSQL);
    echo "<p strong>Stock level updated successfully!";
}

//if a database error is returned, display an order error message
else
{
echo "<p>Sorry there has been an error with your product update";
echo "Go back to <a href=editstock.php>Edit Stock Details</a>";
}
}
//include head layout
include("footlayout.html");
?>

任何想法将不胜感激 . 我几乎在那里找不到任何与这类特殊问题相关的内容 .