Codeigniter is a great php framework, and the one of choice at Papertank. As with any framework code though, sometimes things just don’t work the way you want them to…

Hopefully this post will help any other programmers who come across the same issue – Codeigniter not adding particular products to the shopping cart. In my experience, this is caused by one of two reasons:

Problem A

The Codeigniter Shopping Cart library uses sessions to save your basket, and by adding lots of products or products with various options, this session can get exhausted pretty quickly.

Solution

The first thing to try, if you’ve not already, is to try switching to using your web app’s database for session storage. As well as allowing more information per session, this can increase security.

Before you go changing the config.php file, you’ll want to set up the right table in your database as so:

CREATE TABLE IF NOT EXISTS  `ci_sessions` (
	session_id varchar(40) DEFAULT '0' NOT NULL,
	ip_address varchar(45) DEFAULT '0' NOT NULL,
	user_agent varchar(120) DEFAULT NULL,
	last_activity int(10) unsigned DEFAULT 0 NOT NULL,
	user_data text DEFAULT NULL,
	PRIMARY KEY (session_id),
	KEY `last_activity_idx` (`last_activity`)
);

Now, you’ll want to update the config.php file, usually found in application/config/config.php so that the session library uses the database option. Also, just incase you decided to use a different name for the database table, you can chance this here too.

$config['sess_use_database'] = TRUE;

Problem B

If that didn’t fix your problem, check your error log for more information. For me, there was an issue with product names having invalid characters – in my case a ‘.’

ERROR - 2012-06-26 09:51:27 --> An invalid name was submitted as the product name: Urinal Blocks 1.1Kg The name can only contain alpha-numeric characters, dashes, underscores, colons, and spaces

Solution

To fix this problem, you’ll need to overwrite the default Shopping Cart class – CI_Cart – so that it no longer rejects particular names. In your application/libraries folder, add a file called MY_Cart.php with the following code, or download from https://gist.github.com/16f99e4a38386fac461e:

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

class MY_Cart extends CI_Cart {
 
  public $CI;

  function __construct()
  {
    parent::__construct();

    $this->CI =& get_instance();

  } 
  
	function format_number($n = '')
	{
		if ($n == '')
		{
			return '';
		}
	
		// Remove anything that isn't a number or decimal point.
		$n = trim(preg_replace('/([^0-9.])/i', '', $n));
	
		return number_format($n, 2, '.', '');
	}
	
	/**
	 * Insert
	 *
	 * @access	private
	 * @param	array
	 * @return	bool
	 */
	function _insert($items = array())
	{
		// Was any cart data passed? No? Bah...
		if ( ! is_array($items) OR count($items) == 0)
		{
			log_message('error', 'The insert method must be passed an array containing data.');
			return FALSE;
		}

		// --------------------------------------------------------------------

		// Does the $items array contain an id, quantity, price, and name?  These are required
		if ( ! isset($items['id']) OR ! isset($items['qty']) OR ! isset($items['price']) OR ! isset($items['name']))
		{
			log_message('error', 'The cart array must contain a product ID, quantity, price, and name.');
			return FALSE;
		}

		// --------------------------------------------------------------------

		// Prep the quantity. It can only be a number.  Duh...
		$items['qty'] = trim(preg_replace('/([^0-9])/i', '', $items['qty']));
		// Trim any leading zeros
		$items['qty'] = trim(preg_replace('/(^[0]+)/i', '', $items['qty']));

		// If the quantity is zero or blank there's nothing for us to do
		if ( ! is_numeric($items['qty']) OR $items['qty'] == 0)
		{
			return FALSE;
		}

		// --------------------------------------------------------------------

		// Validate the product ID. It can only be alpha-numeric, dashes, underscores or periods
		// Not totally sure we should impose this rule, but it seems prudent to standardize IDs.
		// Note: These can be user-specified by setting the $this->product_id_rules variable.
		if ( ! preg_match("/^[".$this->product_id_rules."]+$/i", $items['id']))
		{
			log_message('error', 'Invalid product ID.  The product ID can only contain alpha-numeric characters, dashes, and underscores');
			return FALSE;
		}

		// --------------------------------------------------------------------

		// Validate the product name. It can only be alpha-numeric, dashes, underscores, colons or periods.
		// Note: These can be user-specified by setting the $this->product_name_rules variable.
		/*
if ( ! preg_match("/^[".$this->product_name_rules."]+$/i", $items['name']))
		{
			log_message('error', 'An invalid name was submitted as the product name: '.$items['name'].' The name can only contain alpha-numeric characters, dashes, underscores, colons, and spaces');
			return FALSE;
		}
*/

		// --------------------------------------------------------------------

		// 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;
		}

		// --------------------------------------------------------------------

		// We now need to create a unique identifier for the item being inserted into the cart.
		// Every time something is added to the cart it is stored in the master cart array.
		// Each row in the cart array, however, must have a unique index that identifies not only
		// a particular product, but makes it possible to store identical products with different options.
		// For example, what if someone buys two identical t-shirts (same product ID), but in
		// different sizes?  The product ID (and other attributes, like the name) will be identical for
		// both sizes because it's the same shirt. The only difference will be the size.
		// Internally, we need to treat identical submissions, but with different options, as a unique product.
		// Our solution is to convert the options array to a string and MD5 it along with the product ID.
		// This becomes the unique "row ID"
		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
			$rowid = md5($items['id']);
		}

		// --------------------------------------------------------------------

		// Now that we have our unique "row ID", we'll add our cart items to the master array

		// let's unset this first, just to make sure our index contains only the data from this submission
		unset($this->_cart_contents[$rowid]);

		// Create a new index with our new row ID
		$this->_cart_contents[$rowid]['rowid'] = $rowid;

		// And add the new items to the cart array
		foreach ($items as $key => $val)
		{
			$this->_cart_contents[$rowid][$key] = $val;
		}

		// Woot!
		return TRUE;
	}
	 
}

If you look closely, you’ll notice what we’ve done here is actually comment out the specific section that validates the product name. Be careful with this, of course, but when you re-try adding your product, hopefully your issue should be solved.