Exp:resso Store discount extension

ext.store_discount.php

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

/**
 * Store Discount Extension
 *
 * @package     ExpressionEngine
 * @subpackage  Addons
 * @category    Extension
 * @author      Eli Van Zoeren
 * @link        http://elivz.com
 */

class Store_discount_ext {

    public $settings        = array();
    public $description     = 'Apply quantity-based discounts to Exp:resso Store';
    public $docs_url        = 'http://elivz.com';
    public $name            = 'Store Discount';
    public $settings_exist  = 'n';
    public $version         = '1.0';

    private $EE;

    /**
     * Constructor
     *
     * @param   mixed   Settings array or empty string if none exist.
     */
    public function __construct($settings = '')
    {
        $this->EE =& get_instance();
        $this->settings = $settings;
    }

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

    /**
     * Activate Extension
     *
     * This function enters the extension into the exp_extensions table
     *
     * @see http://codeigniter.com/user_guide/database/index.html for
     * more information on the db class.
     *
     * @return void
     */
    public function activate_extension()
    {
        // Setup custom settings in this array.
        $this->settings = array();

        // Add hooks
        $data = array(
            'class'     => __CLASS__,
            'method'    => 'update_cart',
            'hook'      => 'store_cart_update_end',
            'settings'  => serialize($this->settings),
            'priority'  => 10,
            'version'   => $this->version,
            'enabled'   => 'y'
        );

        $this->EE->db->insert('extensions', $data);
    }

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

    /**
     * Disable Extension
     *
     * This method removes information from the exp_extensions table
     *
     * @return void
     */
    function disable_extension()
    {
        $this->EE->db->where('class', __CLASS__);
        $this->EE->db->delete('extensions');
    }

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

    /**
     * Update Extension
     *
     * This function performs any necessary db updates when the extension
     * page is visited
     *
     * @return  mixed   void on update / false if none
     */
    function update_extension($current = '')
    {
        if ($current == '' OR $current == $this->version)
        {
            return FALSE;
        }

        $this->EE->db->where('class', __CLASS__);
        $this->EE->db->update(
                    'extensions',
                    array('version' => $this->version)
        );
    }

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

    /**
     * Responds to the store_cart_update_end hook in Exp:resso Store
     * to apply a discount to each product, as needed
     *
     * @return array of cart items
     */
    function update_cart($cart_contents)
    {
        $this->EE->load->helper(array('store'));

        // Get the number of products currently in the user's cart
        $count = count($cart_contents['items']);

        // Only apply the discount if there is more than one item
        if ($count > 1)
        {
            // Take $10 off all but the first product
            // This calculation can easily be adjusted as needed
            $discount = ($count - 1) * 10;

            // Add the quantity discount to any existing discount (promo code)
            $cart_contents['order_discount_val'] += $discount;
            // Make sure we don't end up with a negative total
            if ($cart_contents['order_discount_val'] > $cart_contents['order_subtotal_val'])
            {
                $cart_contents['order_discount_val'] = $cart_contents['order_subtotal_val'];
            }
            $cart_contents['order_discount'] = store_format_currency($cart_contents['order_discount_val']);

            // Update the cart total to reflect the new discount
            $cart_contents['order_total_val'] = $cart_contents['order_subtotal_val'] - $cart_contents['order_discount_val'];
            $cart_contents['order_total'] = store_format_currency($cart_contents['order_total_val']);
        }

        return $cart_contents;
    }
}

/* End of file ext.store_discount.php */
/* Location: /system/expressionengine/third_party/store_discount/ext.store_discount.php */

Thanks for the response guys.
I was trying with one product, opposed to multiple products. What I require is when a user orders 3 of the same product they would receive a discount.

I don't know PHP at all so don't really know what needs to be changed to achieve the above. I think I probably need to change line 118 somehow in order to get the quantity of items, instead of the items themselves.

The way it currently works, every product after the first one gets a $10 discount. If you wanted the discount to only apply to multiples of the SAME product, you would need to add some slightly more complex logic to loop through $cart_contents['items'], checking the SKU number of each product. You have a lot of leeway with how you calculate the discount... the point of this code is just to give people a boilerplate so they don't need to track down the correct hook and figure out which variables to update after the discount is calculated.

Ha, okay so it is a little more complicated than I just outlined. Shows I know nothing about development.

Right... this is a starting point for developing your own discount extension. If you need a click-and-play interface for discounts, you'll probably need to wait until Exp:resso adds it to Store, or use a different e-commerce add-on (CartThrob has very flexible discounting, although at the expense of a more complex system all around).

Yeah I really should start learning as it will make things a lot easier.
Thanks for this extension Eli it will work as a great starting point. I will ask a mate of mine to have a look and show me how we can extend the code to what I need. I will gist the result when it is done.

Cheers
Dan

Dan.. try something like this (untested, may be some slight errors):

foreach ($cart_contents['items'] as $item)
{
    if ($item['item_qty'] >= 3)
    {
         $cart_contents['order_discount_val'] += 10;
    }
}

then add the rest of the code from above:

        if ($cart_contents['order_discount_val'] > $cart_contents['order_total_val'])
            $cart_contents['order_discount_val'] = $cart_contents['order_total_val'];
        $cart_contents['order_discount'] = store_format_currency($cart_contents['order_discount_val']);

        // Update the cart total to reflect the new discount
        $cart_contents['order_total_val'] = $cart_contents['order_subtotal_val'] - $cart_contents['order_discount_val'];
        $cart_contents['order_total'] = store_format_currency($cart_contents['order_total_val']);

        return $cart_contents;

That should add a $10 discount for every item which has qty >= 3. Notice all the variables are exactly the same as what you use in the template (item_qty, order_total etc).

Works great thanks guys.