How can I populate one list box from the selection of another list box?

[shure2]

Hi,

 

I have a list box that reads category names from the category table. I want to select a category name and populate the product list box with the names of products in the category.

 

I have the code to populate the category listbox and the sql to populate the product listbox, but i'm not sure how to put them together (I guess calling a seperate php file and then passing the values back somehow using a form? - probably wrong!)

 

CODE FOR SELECTING PRODUCT CATEGORY:

<p>Select the product category:<br />
                        <select name="prodcategory" onchange="javascript: form.action='reportmanual_getcategoryproducts.php';">
                            
                            <?php
                            $selectProductCatQuery = "SELECT * FROM category where userid = '".$_SESSION['userid']."' ORDER BY catname";
                            $selectProductCatResult = mysql_query($selectProductCatQuery) or die(mysql_error());
                            
                            while($row1ProductCat=mysql_fetch_array($selectProductCatResult))
                            {
                                echo '<option value="'.$row1ProductCat['catname'].'">'.$row1ProductCat['catname'].'</option>'; 
                            }
                            ?>
                        </select>

 

CODE FOR SELECTING PRODUCT (need help on this bit please):

$query = "SELECT * FROM product where userid = '".$_SESSION['userid']."' and categoryname = '".$_GET['prodcategory']."' ORDER BY 
$result = mysql_query($query) or die(mysql_error());

//I need to get the values from the sql and pass them back to the product select box i have

 

[shure2]

I have created a listbox that populates the product names on a seperate page (seen below), but I want the two list boxes to be on the same page, I don't mind if the page refreshes when the category is selected (to avoid javascript)

 

$query = "select * from product where prodcategory = '".$_GET['prodcategory']."' and userid = '".$_SESSION['userid']."'";
        $result = @mysql_query($query, $connection)or die ("Unable to perform query<br>$query");

        ?>
        <select name="dddd">
            <?php
        while($row=mysql_fetch_array($result))
            {
                echo '<option value="'.$row['prodid'].'">'.$row['prodname'].'</option>';
                echo 'hello';
            }
        
        //exit();
        ?>
        </select>