extending cart's update function to accept new price and options

[eluser]snoo[/eluser]
Hi all,

Due to my items setup configuration, which is to list every possible attribute for an item as an individual item, I need to let my cart->update() accept new options and prices. Essentially, cart->update() becomes remove, then add new item to cart. Also added sorting so I can maintain the cart item order. So I tried to extend the cart library. Everything is working fine, but this is the first time I write extension, please let me know if I'm doing this right. Following in my code, thanks much for any input!

Code:

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class MY_Cart extends CI_Cart {
    
    function __construct(){
        parent::__construct();
        
        // accept () and * in item name
        $this->product_name_rules = '\*\(\)\-_ a-z0-9';
  
    }

function _update($items = array())
{
  // Without these array indexes there is nothing we can do
  if ( ! isset($items['qty']) OR ! isset($items['rowid']) OR ! isset($this->_cart_contents[$items['rowid']]))
  {
   return FALSE;
  }
  
  // create new rowid
  if (isset($items['options']) AND count($items['options']) > 0)
  {
   $rowid = md5($items['id'].implode('', $items['options']));
  }
  else
  {
   // No options were submitted so we simply MD5 the product ID.
   // Technically, we don't need to MD5 the ID in this case, but it makes
   // sense to standardize the format of array indexes for both conditions
   if(isset($items['id']))
   {
    $rowid = md5($items['id']);
   }
  }
  
  if(isset($rowid))
  {
   // save current cart item
   $current_cart_item = $this->_cart_contents[$items['rowid']];
  
   // save current order
   $current_order = $this->_preserve_cart_order($this->_cart_contents);

   // remove current cart with old rowid
   unset($this->_cart_contents[$items['rowid']]);

   // create new array with new rowid
   $this->_cart_contents[$rowid] = $current_cart_item;

   // return order key with old rowid
   $order_key = array_search($items['rowid'], $current_order);
  
   // replace old rowid with new rowid in order array
   $current_order[$order_key] = $rowid;

   // reorder cart
   $this->_cart_contents = $this->_restore_cart_order($this->_cart_contents, $current_order);
  }
  else
  {
   $rowid = $items['rowid'];
  }
  
  
  if(isset($items['price'])){
   // Prep the price.  Remove anything that isn't a number or decimal point.
   $items['price'] = trim(preg_replace('/([^0-9\.])/i', '', $items['price']));
   // Trim any leading zeros
   $items['price'] = trim(preg_replace('/(^[0]+)/i', '', $items['price']));

   // Is the price a valid number?
   if ( ! is_numeric($items['price']))
   {
    log_message('error', 'An invalid price was submitted for product ID: '.$items['id']);
    return FALSE;
   }
   else
   {
    $this->_cart_contents[$rowid]['price'] = $items['price'];
   }
  }
  // Prep the quantity
  $items['qty'] = preg_replace('/([^0-9])/i', '', $items['qty']);

  // Is the quantity a number?
  if ( ! is_numeric($items['qty']))
  {
   return FALSE;
  }

  // Is the new quantity different than what is already saved in the cart?
  // If it's the same there's nothing to do
  if ($this->_cart_contents[$rowid]['qty'] == $items['qty'])
  {
   return FALSE;
  }

  // Is the quantity zero?  If so we will remove the item from the cart.
  // If the quantity is greater than zero we are updating
  if ($items['qty'] == 0)
  {
   unset($this->_cart_contents[$rowid]);
  }
  else
  {
   $this->_cart_contents[$rowid]['qty'] = $items['qty'];
  }
  
  

  return TRUE;
}

function _preserve_cart_order($cart)
{
  $cart_order = array();
  foreach($cart as $key=>$index)
  {
   $cart_order[] = $key;
  }
  return $cart_order;
}

function _restore_cart_order($cart,$cart_order)
{
  $ordered = array();
  foreach($cart_order as $key)
  {
   if(array_key_exists($key,$cart))
   {
     $ordered[$key] = $cart[$key];
     unset($cart[$key]);
   }
  }
  return $ordered + $cart;
}

  
}