BOGO Discount for Zen Cart

A Zen Cart™ discounting module for bulk purchases.

My Better Together module solves a particular problem: allowing you to offer a "Buy One Get One Free" discount on particular items or categories of items.

But what if what you want is Buy One, Get One Free across the entire cart? Or Buy Two, Get One free, or Buy Two, Get One Half off? This is what BOGO does.

The BOGO Discount extension permits you to offer discounts that are structured as:

Buy <M> items, get a discount on <N> items of <X> percent or dollars each.

BOGO settings are global and apply to all your products. Specific exclusions may be created, but otherwise the settings are universally applied. If you do not want all (or most of) your products subject to the rule Buy <M> items, get a discount on <N> items, look at Better Together instead.

Background: See the Zen Cart Matrix-o-discounts

Example Discounts: I have provided several examples of Zen Cart BOGO Discount discounts.

Relevance: Zen Cart™ 1.3.5 - 1.3.9, 1.5.x

Current Version: 1.3 (version history)

Support Thread: My commercial software is not supported on the Zen Cart forum. Please email me questions instead.

Cost: $25 (Note: this low price covers software only for self-installation.)



Would you like to ask me questions before buying? I'm happy to help likely purchasers make the right decision. Please use my contact form.

Installed Cost: $125.00 (Professional installation by That Software Guy)

Installation Difficulty: Easy

Installation Instructions: click here

Tax Notes: Notes on tax handling

Buy: Buy BOGO Discount!
Pre-purchase questions? No problem! Just Please contact me with your question.

FAQ: click here

Configuration: BOGO is configured on the Admin > Modules > Order Total screen. A single configuration is used for the entire cart; if you want to selectively offer buy-one get-one discounts or buy-two-get-one discounts without needing to make code changes by hand, you may wish to consider Better Together or Combination Discounts. Alternatively, you can do make some code changes described in Limited BOGO.

Marketing Text: click here

Add-Ons:
Normally, the BOGO discount is not shown until the second page of checkout. If you want to show the discount on the shopping cart page, look at Discount Preview.

Alternatives: BOGO Discount configuration applies to the entire cart - all items are set to buy-one, get-one, or buy-two, get-one (or whatever your configuration specifies). (There are ways to restrict this further, but they require code changes; they cannot be done using an admin panel. See Limited BOGO.) Sometimes this is not a good match for a shop owner's requirements; if you want to selectively offer buy-one get-one discounts, take a look at Better Together. If your discounts require the purchase of more than one item (for example, buy-two, get one, etc.), take a look at Combination Discounts or Zen Cart Free Gift Chooser.

Bugs: click here

---

Overview:

Detailed Description:

1. Configuration
   
   
   BOGO Discount is configured through the Admin interface (Admin > Modules > Order Total > BOGO Discount).
   
   The image above shows a shop which gives a "Buy 2 Get 1 100% off" (i.e. "Buy 2 Get 1 Free") for all items in the store.
   
   Items which are counted to meet the condition ("Buy 2") are counted from most to least expensive, and items which are to be discounted ("Get 1 Free") are from least to most expensive. So BOGO Discount always discounts the least expensive items possible.
   
   Discount Basis has five possible values:
   • Same Item
   • Same Item, Same Attributes
   • Same Parent Category
   • Same Top Level Category
   • No Restriction
   Using the example below:
   
   

   Men's Clothing 
        |
        ---->  Shirts
               |
               -------> shirt A     
                        shirt B
                        shirt C 
        ---->  Pants 
               |
               -------> pants A     
                        pants B
                        pants C 
        ---->  Neckwear 
               |
               -------> Bow Ties 
                        |
                        -------> bow tie A     
                                 bow tie B
               -------> Neck Ties 
                        |
                        -------> necktie A     
                                 necktie B
   Women's Clothing 
        |
        ----> Dresses  
               |
               -------> dress A     
                        dress B
   
   

   Let's assume for this example that Buy This Many is 1, and Get This Many is 1.
   
   If Discount Basis was "Same Item" and one shirt A size Medium and one shirt A size Large were purchased, the less expensive shirt would be discounted.
   
   If Discount Basis was "Same Item, Same Attributes" and one shirt A size Medium and one shirt A size Large were purchased, there would be no discount.
   If two size Medium were purchased, one of the shirts would be discounted.
   
   If Discount Basis was "Same Parent Category" and shirt A and shirt B were purchased, the less expensive shirt would be discounted.
   If shirt A and pants A were purchased, there would be no discount.
   
   If Discount Basis was "Same Top Level Category" and shirt A and pants A were purchased, the less expensive item would be discounted.
   If shirt A and dress A were purchased, there would be no discount.
   
   If Discount Basis was "Same Top Level Category" and shirt A and dress A were purchased, the less expensive item would be discounted.
   
   Note that your only options for categories are top level category and parent category. So the category "Neckwear" (which is the grandparent category of bow tie A, bow tie B, necktie A and necktie B) would not be considered a parent category.
   
   Specifying "include tax = true" will gross the discount up by the amount of tax that would have been paid on the goods prediscount. This is appropriate for shops under a price inclusive sales tax system, such as the UK VAT. Specifying Re-calculate tax = Standard will recalculate the entire tax based on the original subtotal minus the bogo discount. Even more information about tax is provided at the bottom of this file.
   
   
2. User Exits
   Some shops will want to further customize their discounting policy. Additional user exits are provided to permit the following customizations:
   • Exclude certain categories from discounting.
   • Exclude certain products from discounting.

   
   Specifically:

   • The function exclude_category() shows you how to add categories to a list of categories to not be discounted. You may specify a parent category id.
   • The function exclude_top_category() shows you how to add categories to a list of top level categories to not be discounted. You may specify a top level category id.
   • The function exclude_product() shows you how to add products to a list of products to not be discounted.
   
   Each of these functions contains a simple example of how to use it using item and category numbers like 99999, 99998, etc. See the FAQ below for more examples.
   
   The user exits are within the BOGO Discount contribution, in includes/modules/order_total/ot_bogo_discount.php
   
   BOGO Discount discounts off the *gross* price of the goods. This can result in a larger than expected discount if other discounts are added (such as coupons or group discounts), so bear this in mind when creating your discount strategy.
   
   
3. Checkout Page User Interface
   
   BOGO Discount is an "Order Total" module, which means that by default, the discount is not shown until the second page of checkout (Payment Information). However, using the Discount Preview module will allow you to show the discount in the shopping cart.
   
   
   Depending on your configuration, the second page of checkout will look something like this:
   
   
   
   

Installation Instructions:

1. Back up everything! Try this in a test environment prior to installing it on a live shop.
2. If you already have the BOGO Discount module installed, please deinstall your old copy by going to Admin > Modules > Order Total, selecting "BOGO Discount" and pressing the "Remove" button. Make a note of your settings so you can apply them to the new version.
3. Copy the contents of the unzipped folder to the root directory of your shop. NOTE that these files assume your template name is "custom," so any file with "custom" in its path name will need to be renamed if you are using a different template name. Note: If you are using Zen Cart 1.5.5 or higher, your template name will be "responsive_classic" if you have not changed it.
4. Login to admin and in Modules > Order Total you will see 'BOGO Discount' listed along with all the other modules available.
5. Click on 'BOGO Discount' to highlight the module and click on 'Install'
6. Decide on the parameters you wish to use. The easiest way to do this is to open a shopping cart in another window, and just try different discounting models. The discounts are shown on the second step of checkout in "Your Total" under "BOGO Discount."
7. Customization: If you have a single discounting policy for your shop, you're all set. If you wish to tailor the policy, you will have to add code to the user exits as described above.
8. If you wish, follow the guidelines in marketing to advertise your discounts.

Optional Installation Instructions:

1. I highly recommend Discount Preview with all my discounting modules. Without Discount Preview, your customers cannot see the price reductions they are entitled to until the second page of checkout (checkout confirmation). Obviously this is a disadvantage, particularly for new customers who need to go through the additional step of creating an account before they can see this information. Sometimes seeing is believing, so here's a video showing Discount Preview in action.

Marketing

<?php 
require($template->get_template_dir('/tpl_bogo_marketing.php',DIR_WS_TEMPLATE, 
   $current_page_base,'templates'). '/tpl_bogo_marketing.php');
?>

  if ($discount->check() > 0) {

  if ( ($discount->check() > 0) &&
       (!$discount->exclude_category($current_category_id)) ) {

  if ( ($discount->check() > 0) &&
       (!$discount->exclude_product($_GET['products_id'])) ) {

More Examples

"Buy one, get another identical item half off."

"Buy one, get another from the same category free."

"Buy any one, get three more lesser or equal value half off."

BOGO and Discount Preview

   function  setup() {
      $this->allowed_categories = [19, 62, 50]; // only allow BOGO on these categories
   }

   function  setup() {
      $this->set_cat_equivalent(19, 62, 50); // Group these categories 
   }

Example 1:
Cart contains 2 Mouse, 1 Keyboard
No changes to setup() function.
Discount $0

Example 2: 
Cart contains 2 Mouse, 1 Keyboard 
setup() function contains $this->set_cat_equivalent(9, 8);
Discount $39.99

Combining Grouped And Limited BOGO

   function  setup() {
      $this->allowed_categories = [19, 62, 50, 12, 17]; // only allow BOGO on these categories
      $this->set_cat_equivalent(19, 62, 50); // Group these categories 
   }

• Buy any 2 category 19, 62 or 50, get 1 from category 19, 62 or 50 free
• Buy any 2 category 12, get 1 category 12 free
• Buy any 2 category 17, get 1 category 17 free
• All other categories not discounted.

   function  setup() {
      $this->allowed_categories = [19, 62, 50, 12, 17]; // only allow BOGO on these categories
      $this->set_cat_equivalent(19, 62, 50); // Group these categories 
      $this->set_cat_equivalent(12, 17); // Group these categories 
   }

• Buy any 2 category 19, 62 or 50, get 1 from category 19, 62 or 50 free
• Buy any 2 category 12 or 17, get 1 category 12 or 17 free
• All other categories not discounted.

Files

(new) includes/languages/english/modules/order_total/ot_bogo_discount.php
(new) includes/modules/order_total/ot_bogo_discount.php

Major Versions

• 1.3 07/01/2022 Added allowed_categories and set_cat_equivalent.
• 1.2 12/21/2018 PHP 7
• 1.1 03/04/2013 Fixed issue with multiple discounts; code inspection; checked for exclusions in marketing text
• 1.0 09/01/2012 First Release

Bugs

• For recalculate tax = Standard, carts using Edit Orders 4.3.1 will need to change the process() function in the code file in includes/modules/order_total as follows:
  Change

                 if ($this->calculate_tax != 'VAT') {
                    $order->info['total'] -= $od_amount[$key];
                 }
  

  to

                 if (!IS_ADMIN_FLAG) {
                    if ($this->calculate_tax != 'VAT') {
                       $order->info['total'] -= $od_amount[$key];
                    }
                 }
  

• In version 1.0, for Discount Basis other than No Restriction, BOGO would stop after the first discount.
• Users wishing to sort native discounts (such as Coupons or Group Discounts) after my discounts, with tax recalculation, should look at this page.

FAQ

1. Go to Admin > Modules > Order Total. Do you see BOGO Discount? If not, then you haven't installed it. Follow the README.
2. If you do see it, the circle at the right hand end of the row for BOGO Discount should be green. If it's not green, reinstall it.
3. Click on BOGO Discount. The Discount Amount field is numeric. Do not use dollar or percent signs in this field.
4. If you're using Discount Basis "Same Parent Category" or "Same Top Level Category," see the previous FAQ question.
5. Re-read my Guide to Mod Installation on Zen Cart.

    function exclude_category($category) {
        switch($category) {
           case 11:
           case 12:
                return false;
        }
        return true;
    }

    function exclude_category($category) {
        switch($category) {
           case 7:
           case 8:
                return true;
        }
        return false;
    }

    function exclude_product($prid) {
        $id = (int)$prid;
        switch($id) {
           case 17:
           case 19:
                return false;
        }
        return true;
    }

    function exclude_product($prid) {
        $id = (int)$prid;
        switch($id) {
           case 12:
           case 13:
                return true;
        }
        return false;
    }

  if ($discount->check() > 0) {

  if ( ($discount->check() > 0) &&
       (!$discount->exclude_category($current_category_id)) ) {

  if ( ($discount->check() > 0) &&
       (!$discount->exclude_product($_GET['products_id'])) ) {

Extensions

• Show BOGO Discount on the shopping cart page using Discount Preview