How To Limit Product Quantity In Product_info With $messagestack

[beachkitty85]

I am trying to add $messagestack errors based on the product quantity and (at a later stage) the attribute option value. This is so I can limit the quantity based on which attribute is selected. I've duplicated the $messageStack code from create_account.php, but I just can't get it to work. I've added this to the page top:

$process = false;
if (isset($HTTP_POST_VARS['action']) && ($HTTP_POST_VARS['action'] == 'process')) {
$process = true;

$quantity = tep_db_prepare_input($HTTP_POST_VARS['quantity']);

if (strlen($quantity) > 1) {
$error = true;
$messageStack->add('cart_quantity', 'Error!');
}

if ($error == false) {
$sql_data_array = array('qty' => $quantity);

$qty = $quantity;
tep_session_register('qty');

}
}

and changed the form to this: (added a hidden field just like in create_account.php)

<?php echo tep_draw_form('cart_quantity', tep_href_link(FILENAME_PRODUCT_INFO, tep_get_all_get_params(array('action')) . 'action=add_product'), 'post', 'enctype="multipart/form-data" onsubmit="return check_form(cart_quantity);"') . tep_draw_hidden_field('action', 'process'); ?>

And this where the error shoud display:

<?php
 if ($messageStack->size('cart_quantity') > 0) {
?>
<table class="error">
<tr>
	<td><?php echo $messageStack->output('cart_quantity'); ?></td>
</tr>
</table>
<?php
 }
?>

 

Could someone please help out? Also, if anyone knows how I could implement validation based on attribute option values, please let me know.