使用两个外键将数据插入一个表中

Question

I have two tables (for POS system) named: purchase and product. The columns of the purchase table are: poid (PK, auto_increment), prodid (FK), poquantity. The columns of the product table are: prodid (PK, auto_increment), prodname, price, quantity. I want to insert the data into the purchase table.

Here are the form codes:

<?php
  $tbl_name="product"; 
$con = mysql_connect("localhost","root","");
if (!$con)
 {
 die('Could not connect: ' . mysql_error());
 }

mysql_select_db("pos", $con);
$prodid=$row['prodid'];
$result = mysql_query("SELECT prodname FROM product where prodid = '$prodid'");

 echo "<form action='addprodcon.php?id=$row[prodid]' method='POST'>
  <input name='add' type='submit' value='ADD'></br></br>
  </form>";
  ?>

Here are the insert codes I have created:

<?php
include('includes/dbcon.php');

$prodid = $_GET['prodid'];
$sql1="SELECT prodid FROM product WHERE prodid='$prodid'";

if(mysql_query($sql1))
{
$sql2="INSERT INTO purchase (`prodid`, `poquantity`) 
VALUES
('$prodid','$_POST[poquantity]')";
 }
if (mysql_query($sql2))
{
    // Success
 if ( $poquantity > $_POST['quantity'])
  {
  echo "You already reached the maximum quantity";
  }
}
else 
{
    die('Error on query 2');
}


?>

Whenever I hit the submit button, it say: Unidentified index: prodid Help or suggestions, please? I'm still a student learning about PHP. Thanks! :)

Answer 1

Your form action is addprodcon.php?id=$row[prodid]. It is $_GET['id'], and not $_GET['prodid'] that you should use on line 4 of addprodcon.php.