Notifier/Observer problem editing Real World Example 1

[dale88]

<?php
/**
 * Observer class used to add a free product to the cart if the user spends more than $x
 *
 */
class freeProduct extends base {
  /**
   * The threshold amount the customer needs to spend.
   * 
   * Note this is defined in the shops base currency, and so works with multi currency shops
   *
   * @var decimal
   */
  var $freeAmount = 50;
  /**
   * The id of the free product.
   * 
   * Note. This must be a true free product. e.g. price = 0 Also make sure that if you don't want the customer
   * to be charged shipping on this, that you have it set correctly.
   *
   * @var integer
   */
  var $freeProductID = 57;
  /**
   * constructor method
   * 
   * Attaches our class to the $_SESSION['cart'] class and watches for 2 notifier events.
   */
  function freeProduct() {
    $_SESSION['cart']->attach($this, array('NOTIFIER_CART_ADD_CART_END', 'NOTIFIER_CART_REMOVE_END'));
  }
  /**
   * Update Method
   * 
   * Called by observed class when any of our notifiable events occur
   *
   * @param object $class
   * @param string $eventID
   */
  function update(&$class, $eventID, $paramsArray = array()) {
  
    if ($eventID == 'NOTIFIER_CART_REMOVE_END' && (isset($_SESSION['freeProductInCart']) && $_SESSION['freeProductInCart'] == TRUE ))
  {
    if (!$_SESSION['cart']->in_cart($this->freeProductID))
    {
      $_SESSION['userRemovedFreeProduct'] = TRUE;
    }
  }

  if (!isset($_SESSION['userRemovedFreeProduct']) || $_SESSION['userRemovedFreeProduct'] != TRUE) 
  {
    if ($_SESSION['cart']->show_total() >= $this->freeAmount && !$_SESSION['cart']->in_cart($this->freeProductID) ) // when this statement is removed i get an error  
    {    
      
      $_SESSION['cart']->add_cart($this->freeProductID);
      $_SESSION['freeProductInCart'] = TRUE;  
    }
  }
 
  if ($_SESSION['cart']->show_total() < $this->freeAmount && $_SESSION['cart']->in_cart($this->freeProductID) ) 
  {
    $_SESSION['cart']->remove($this->freeProductID);
  }

 
  if ($_SESSION['cart']->in_cart($this->freeProductID)) 
  {
    $_SESSION['cart']->contents[$this->freeProductID]['qty'] = 1;
  }
   
  }  
}

?>

thanks man. that is the code on wiki. "if ($_SESSION['cart']->show_total() >= $this->freeAmount && !$_SESSION['cart']->in_cart($this->freeProductID) ) " when that statement is remove i get an error the page wont load properly.