tg11 & others,
I have a question on the code that you posted. I understand that everyone used the code and it is working. For some odd reason it is making my website blank. when I take out the code, my whole website is back the way it was. When I checked out the code I see some similar code when I download the product matrix grid module except it does not solve the problem regarding the mixed options for multiple quantities error. The current code gives the end user options in purchasing the single product but they will receive the multiple quantities error. The code that I have in my shopping cart is:
Lines: 1545 to 1588
Code:
/**
* Method to calculate item quantity, bounded the mixed/min units settings
*
* @param boolean product id of item to check
* @return deciaml
*/
function in_cart_mixed($products_id) {
global $db;
// if nothing is in cart return 0
if (!is_array($this->contents)) return 0;
// check if mixed is on
// $product = $db->Execute("select products_id, products_quantity_mixed from " . TABLE_PRODUCTS . " where products_id='" . (int)$products_id . "' limit 1");
$product = $db->Execute("select products_id, products_quantity_mixed from " . TABLE_PRODUCTS . " where products_id='" . zen_get_prid($products_id) . "' limit 1");
// if mixed attributes is off return qty for current attribute selection
if ($product->fields['products_quantity_mixed'] == '0') {
return $this->get_quantity($products_id);
}
// compute total quantity regardless of attributes
$in_cart_mixed_qty = 0;
$chk_products_id= zen_get_prid($products_id);
// reset($this->contents); // breaks cart
$check_contents = $this->contents;
while (list($products_id, ) = each($check_contents)) {
$test_id = zen_get_prid($products_id);
if ($test_id == $chk_products_id) {
$in_cart_mixed_qty += $check_contents[$products_id]['qty'];
}
}
return $in_cart_mixed_qty;
}
/**
* Method to calculate item quantity, bounded the mixed/min units settings
*
* @param boolean product id of item to check
* @return deciaml
*/
function in_cart_mixed_discount_quantity($products_id) {
global $db;
// if nothing is in cart return 0
if (!is_array($this->contents)) return 0;
product matrix grid:

My errors:

I am not sure what I am doing wrong. 
Any advice?