PHP MySQL Get material and quantity for an order form

I need to create an order form that has a checkbox for each product in a table and have a quantity box next to each product.
I need to process the products that have been checked and update an orders table with the checked products and the quantity entered.

I don't know how to link the product checkbox to the quantity field.

$sql="select * from tproducts";

$result=mysqli_query($con, $sql) or die(mysqli_error($con));
echo "<table>";
echo "<tr>";
echo "<th>Product Names</th>";
echo "</tr>";
if(mysqli_num_rows($result)>0)
{
echo "<form action=welcome1.php method=post>";
while ($row = mysqli_fetch_array($result))
{
echo "<tr>";
echo '<td><input type="checkbox" value="' . $row['intProductID'] . '" 
name="materialcode[]">' . $row['strProductName'] . "</td>";
echo "<td>Enter Quantity </td>";
echo "<td><input type='text' name='qty[]' value='qty' size=5></td>";  
echo "</tr>";
} 
} 
echo "</table>";
echo '<input type="submit" name="submit" value="submit" />';
echo "</form>";
echo "</html>";