Whats wrong with my add_cart code?!

[enigmabomb]

Hi,

I'm trying to write an observer, and it fails whenever I try to add an item to the cart. See below:

<?php
class platinum extends base 
{
    var $freeProductID = 75837;

    function platinum()
    {
        $_SESSION['cart']->attach($this,array('NOTIFIER_CART_ADD_CART_END'));
    }
    
    function update(&$callingClass, $notifier, $paramsArray) 
    {
        global $db;
        //die($_SESSION['customer_id']);
        $statement = "SELECT `customers_group_pricing` FROM `ch_customers` WHERE `customers_id` = ".(int)$_SESSION['customer_id'];
        $check = $db->Execute($statement);
        if($check->RecordCount() == 1)
            if ($check->fields["customers_group_pricing"]==2)
            {
                //$_SESSION['cart']->add_cart($this->freeProductID,1);
                $_SESSION['cart']->add_cart("75837");            
            }
    }
}
?>