php - データ テーブルの数量の更新

Question

顧客が任意の数量を入力すると在庫が更新され、次の顧客のために現在の金額を維持する注文フォームをセットアップしようとしています。正しいコードを考え出そうとしていますが、今のところうまくいきません。どんなアドバイスでも大歓迎です、ここに私のコードがあります:

<?php
session_start(); //Lets start a session! This is the index page
$_SESSION["access"] = "My_session";
//We need a header right, well here it is?
define ("TITLE", "Products page");
include('templates/header.html');
?>
<h2 class="intro">
    Looking for the perfect widget for the perfect person? Browse through our small but original
    list of products to purchase. Alternatively you can contact us through our contact page and one of our team will get
    back to you as soon as possible.
    WIDGET ORDER FORM Widget Quantity Cost Dehydrated water " /> $ 18.50 Glass Stems " /> $ 28.50

    <?php
    // Get the values from the $_POST array:
    $quantityarray = ((isset($_POST['f_wa']) ? $_POST['f_wa'] : '') || (isset($_POST['f_gl']) ? $_POST['f_gl'] : ''));

    include 'connection.php';

    # Define the SQL statement
    $query = 'Select ProductID, InStock from Inventory ORDER BY ProductID';
    if ($result = mysql_query($query)) {
        while ($row = mysql_fetch_array($result)) {
            $currentnum = $row['InStock'] - $quantityarray[$row['ProductID']];
            $prodid = $row['ProductID'];
            // execute a SQL statement to update the InStock number
            $query = "UPDATE Inventory SET InStock = $currentnum WHERE ProductID=$prodid";
            sendquery($query);
        }
    }

    function sendquery($query)
    {
        if (@mysql_query($query)) {
            print '<p>Table populated.</p>';
        } else {
            print '<p style="color:red;">Error executing SQL statement: <br/>' . mysql_error() . '.</p>

    <p>The statement being run was: ' . $query . '</p>';
        }
    }

    ?>
    <?php
    //To conclude we also need the footer, don't we?.
    include('templates/footer.html');
    ?>