dynamic drop down boxes

[CincoPistolero]

I need to create a form that when I select an option in a dropdown box, it takes the id from that item and uses that id to fill another drop down boxes selections. Getting the initial dropdown info with ID is easy, but I'm not sure how to get the other box to populate.

Below is my code for the drop downs. The first box is populating the correct data, but when something is selected, no matter what it is, the second box always shows the same thing.

Ideally, I'd like the second box either to not show up initially, or have it empty until something is chosen in the first dropdown.

[code]

<?php /* Size Information Query */
$querysize = " SELECT * FROM size where drumID=1 ORDER BY `sizeID` ASC LIMIT 0 , 30 ";
$resultsize = mysql_query($querysize) or die ("Error in query: $querysize. " . mysql_error());
?>
      <select name='size' onChange="if (document.myform.size.selectedIndex != 0) window.open(url = document.myform.size.options[document.myform.size.selectedIndex].value,'_self'); else alert('Please choose from menu.')">
        <option selected>Select Size</option><?php
        while ( $rowsize= mysql_fetch_array($resultsize)){extract($rowsize);
        echo "
        <option value='rhino_new.index.php?sizeID=$sizeID'>$sizeName</option>"
        ;}?>

      </select>
                                                                                    </td>
                    <td width="11%"><b><u><font face="Verdana" color="#ff9c31" size="2">FINISH: </font></u></b></td>
                                                                                    <td width="24%">                   
        <?php
if ($sizeID >0) { ?> 
<?php  /* Finish Information Query */
$queryfinish = " SELECT * FROM finish where sizeID='$sizeID' ORDER BY 'finishID' ASC LIMIT 0, 30 ";
$resultfinish = mysql_query($queryfinish) or die ("Error in query: $queryfinish. " . mysql_error());
?> 
<select name='finish' onChange="if (document.myform.finish.selectedIndex != 0) window.open(url = document.myform.finish.options[document.myform.finish.selectedIndex].value,'_self'); else alert('Please choose from menu.')">
        <option selected>Select Finish</option><?php
        while ( $rowfinish= mysql_fetch_array($resultfinish)){extract($rowfinish);
        echo "
        <option value='rhino_new.index.php?sizeID=$sizeID?finishID=$finishID'>$finishName - $price</option>"
        ;}?>

      </select>
      <?php } else { ?> &nbsp; <?php } ?>
[/code]

[drifter]

I believe you are looking for some javascipt not php

[papaface]

Yeah. Always remember PHP is SERVER-side. Therefore nothing in the browser is done by php.
You need a client-side scripting language i believe such as Javascript.