Quantity Discounts

A Zen Cart™ discounting module for bulk purchases.

Background: See the Zen Cart Matrix-o-discounts

Relevance: Zen Cart™ 1.3.5 and forward

Cost: Free, but donation appreciated

Location: Zen Cart Downloads page, under Pricing Tools.

Download: Quantity Discounts on Zen Cart Downloads Page

Promotional Page Download: free from my website

Current Version: 1.10. Occasionally, new features are documented prior to being publicly available; please check the version history to ensure the feature you want is available in your version.

Changes in 1.3.8: Quantity Discounts requires a patch to run under Zen Cart 1.3.8. Take this function and paste it right above the function calculate_deductions() in the file includes/modules/order_total/ot_quantity_discount.php. Quantity Discounts 1.8 or higher includes this fix.

Support Thread: Quantity Discounts Support Thread

FAQ: click here

Installation: click here

See it Live: Go to my demo shop and add ten of any item to your cart (excluding gift certificates). You will immediately see the discount because of Discount Preview, but without it, you would see the discount on the second page of checkout. Also note the marketing text for Quantity Discounts on the Product Info page. The format shown in example 1 is used.

Add-Ons:
As noted, adding 10 of the same item to the cart displays the discount on the shopping cart page because of Discount Preview.

Here is a sample of the Quantity Discounts promotional page, which is described in this tip.

Bugs: click here

Overview:

This mod permits a shop to define up to five admin specified quantity discount levels on a per-product, per category or total number of items purchased basis. The discounts may be expressed in percentage or currency units. Various user exits are provided to make it easy to extend the mod to meet shop requirements.

The limit of five levels can be exceeded using a simple interface in the code to define additional levels.

Detailed Description:

Configuration
Quantity Discounts is configured through the Admin interface (Admin-> Modules->Order Totals->Quantity Discount).

The image to the left shows a shop which gives 10% off items bought in quantities of 5 or more.

Discount Level 1..5 and Discount Amount 1..5 are fields which contain a set of five discount levels (min. quantity required to get to this level, discount amount) may be specified. The Discount Basis radio buttons determine if quantity required to get to a discount level is counted as bulk purchases of a single item (Total By Item), by purchases within a category (Total By Category) or by the total number of items in the cart (Total Items in Cart). The Discount Units radio buttons allow the units of discount levels to be specified as percent off, currency units off (i.e. dollars off the total), or currency units per item off (i.e. dollars off per item).

Note that the category used is the parent category. This means that when using Total By Category for products in subcategories, the "category" will be the parent subcategory, not the top level category.
```
Men's Clothing 
     |
     ---->  Shirts
            |
            -------> shirt A     
                     shirt B
                     shirt C 
```
In this example, the parent category of "shirt A" is "Shirts," not "Men's Clothing." "Mens' Clothing" would be considered the top level category.

In stores where the first level of categories has products directly underneath it, the top level category and the parent category are the same. If have the ability to reference top level categories is important to your store, you may wish to consider purchasing the Quantity Discounts Extension that does this.

Specifying "include tax = true" will gross the discount up by the amount of tax that would have been paid on the goods pre-discount. 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 quantity discount. Even more information about tax is provided at the bottom of this file.

Counting Method allows discounting by dollars spent rather than units purchased as is normally done. The default value for this field is "items."
User Exits
Some shops will want to further customize their discounting policy. Additional user exits are provided to permit the following customizations:
- Include or exclude certain categories from discounting.
- Include or exclude certain products from discounting.
- Modify the discounts for particular categories if discounting by category.
- Modify the discounts for particular items if discounting by item.
Specifically:
- The function exclude_category() shows you how to add categories to a list of categories to not be discounted. This may be used with any Discount Basis.
- The function exclude_product() shows you how to add products to a list of products to not be discounted. This may be used with any Discount Basis.
- If you are using the Discount Basis "Total By Category," you may customize the discount for a specific category using the function apply_special_category_discount().
- If you are using the Discount Basis "Total By Item," you may customize the discount for a specific item using the function apply_special_item_discount().
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 Quantity Discounts contribution, in includes/modules/order_total/ot_quantity_discount.php.

Quantity Discounts 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.

Checkout Page User Interface
Quantity Discounts 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, it will look something like this:

Notice that "Quantity Discount" is a link, which will show the breakdown of the discount, depending on the Discount Basis you selected on the Admin screen. For instance, if the Discount Basis is "Total Items in Cart," with a Discount Level 1 of "4" and a Discount Amount 1 of "10," you would see this dialog if you clicked the "Quantity Discount" link:

With a Discount Basis of "Total By Category," assuming these items were all in the same category (and the category was "Fish"), you would see this dialog if you clicked the "Quantity Discount" link:

Next, we'll use a Discount Basis of "Total By Item." The original items were all in the same category, and we'll add four more of another item from the same category. The two items have model numbers "BLUEFISH-127" and "REDFISH-492". You would now see this dialog if you clicked the "Quantity Discount" link:
Breaking the five level barrier
Suppose your discounting strategy is as follows:

Level Amount

5 5% off

10 10% off

15 15% off

20 20% off

25 25% off

100 50% off

How do you create that last discount?

Quantity Discounts 1.4 has the answer. In the file includes/modules/order_total/ot_quantity_discount.php, there is a function called setup(). From there, you may add a call to a function to add additional discounting levels and discounts in the following manner:
```
    function  setup() {
       // Add extra levels and discounts here in this manner: 
       // "Buy more than 100 items, get 50 (% or $, as per admin) off" 
       $this->add_extra_level_discount(100, 50); 
    }
```
The behavior of these {level, discount} pairs is identical to those you added in the admin panel. Specifically,
- They will show up as explanatory text in the checkout page user interface
- They will show up in your marketing text

Big Spender vs. Quantity Discounts by Dollars Spent:
Big Spender offers discounting by dollars spent with many more options than Quantity Discounts. If you simply wish to offer a price sensitive discount on the entire cart, you can use Quantity Discounts, but if you want to do things like offer a free gift over a certain level of spending, or have multiple price sensitive offerings which are mutually exclusive, you should check out Big Spender.

Installation Instructions:

Back up everything! Try this in a test environment prior to installing it on a live shop.
If you already have the Quantity Discounts module installed, please deinstall your old copy by going to Admin->Modules->Order Total, selecting "Quantity Discount" and pressing the "Remove" button. Make a note of your settings so you can apply them to the new version.
Copy the contents of the unzipped folder to the root directory of your shop.
Login to admin and in Modules->Order Total you will see 'Quantity Discount' listed along with all the other modules available.
Click on 'Quantity Discount' to highlight the module and click on 'Install'
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 in "Your Total" under "Quantity Discount," which is itself a link that explains the calculation.
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.
If you wish, follow the guidelines in marketing to advertise your discounts.
If you wish, install a Quantity Discounts Promotional Page by following the links at the top of this page.

Marketing

If you would like to have a Quantity Discounts Promotional Page that describes your store quantity discounts as part of your categories sidebox, you may download a sample here.

You can also add any of these examples of marketing code you like to your own product info page. Create your custom template and edit the file tpl_product_info_display.php to add one of the code blocks shown below.

Quantity Discounts Marketing Example 1 Code

<!-- bof Quantity Discounts Contribution Example 1 Marketing Text -->
<?php
  $value = "ot_quantity_discount.php"; 
  include_once(zen_get_file_directory(DIR_WS_LANGUAGES . $_SESSION['language'] . 
          '/modules/order_total/', $value, 'false'));
  include_once(DIR_WS_MODULES . "order_total/" . $value);
  $discount = new ot_quantity_discount();  
  if ($discount->check() > 0) { 
     echo '<div class="content" id="discountPolicy1" 
       style="margin-left:25px; border: 1px solid #000000; width: 300px; padding: 5px; background: #C0C0C0;">';
     echo '<h2>' . STORE_POLICY . '</h2>'; 
     echo $discount->get_html_policy();
     echo '<br /></div>'; 
  }
?>
<!-- eof Quantity Discounts Contribution -->

This creates output that will look something like this:

Quantity Discounts Marketing Example 1 Output

Store Quantity Discount Policy

Buy 2 or more of any item, get 5% off
Buy 5 or more of any item, get 10% off
Buy 10 or more of any item, get 15% off
Buy 50 or more of any item, get 50% off

If you want your discounts to appear in "largest first" order, use get_discount_info (which returns an array) instead of get_html_policy (which returns a string). Then simply reverse sort the array. Since we have each item broken out into an array element, we'll make a table with a single column this time:

Quantity Discounts Marketing Example 2 Code

<!-- bof Quantity Discounts Contribution Example 2 Marketing Text -->
<?php
  $value = "ot_quantity_discount.php"; 
  include_once(zen_get_file_directory(DIR_WS_LANGUAGES . $_SESSION['language'] . 
          '/modules/order_total/', $value, 'false'));
  include_once(DIR_WS_MODULES . "order_total/" . $value);
  $discount = new ot_quantity_discount();  
  if ($discount->check() > 0) {
     echo '<div class="content" id="discountPolicy2">'; 
     echo '<table style="border: 1px solid #999999; background: #000000;">'; 
     echo '<tr><td><h2 style="color: #FFFFFF;">' . STORE_POLICY . '</h2></td></tr>';
     $dislist = $discount->get_discount_info();
     for ($i = 0; $i < sizeof($dislist); $i++) {
       if (($i % 2) == 0) 
            $style = 'bgcolor="#EEE8AA"';
       else 
            $style = 'bgcolor="#D2B48C"';
       echo '<tr ' . $style . '><td>'. $dislist[$i] . "</td></tr>";
     }
     echo '</table>';
     echo '<br /></div>'; 
  }
?>
<!-- eof Quantity Discounts Contribution -->

This produces a result that will look like the following:

Quantity Discounts Marketing Example 2 Output

Store Quantity Discount Policy

Buy 10 or more of any item, get 15% off

Buy 20 or more of any item, get 20% off

Buy 30 or more of any item, get 30% off

What if we want to do something that shows the levels as a range? We can always do this sort of thing:

Quantity Discounts Marketing Example 3 Code

<!-- bof Quantity Discounts Contribution Example 3 Marketing Text -->
<?php
  $value = "ot_quantity_discount.php"; 
  include_once(zen_get_file_directory(DIR_WS_LANGUAGES . $_SESSION['language'] . 
          '/modules/order_total/', $value, 'false'));
  include_once(DIR_WS_MODULES . "order_total/" . $value);
  $discount = new ot_quantity_discount();  
  if ($discount->check() > 0) {
     echo '<div class="content" id="discountPolicy3">'; 
     echo '<table border="1" bgcolor="#FFFF66"><tr><td>Quantity</td><td>Discount</td></tr>'; 
     $dislist = $discount->get_discount_parms();
     for ($i = 0; $i < sizeof($dislist); $i++) {
         echo '<tr><td>' . $dislist[$i]['level']; 
         if ($i == (sizeof($dislist) - 1)) {
            echo " + "; 
         } else { 
            echo " - ";
            echo $dislist[$i+1]['level'] - 1; 
         }
         echo "</td><td>" . $dislist[$i]['discount'] .  "</td></tr>";
     }
     echo '</table>';
     echo '<br /></div>'; 
  }
?>
<!-- eof Quantity Discounts Contribution -->

This produces an output like the following:

Quantity Discounts Marketing Example 3 Output

Quantity	Discount
10 - 19	15%
20 - 99	20%
100 +	50%

If you want to do something close to what the native Quantity Discounts does, which is show each of the prices and the range required to get that price, it can also be done. However, note that this only works for discount units percentage. I also believe that it only makes sense for a Discount Basis of Total By Item, but this restriction is not enforced.

To show final, discounted prices at various quantity levels, you could do something like this:

Quantity Discounts Marketing Example 4 Code

<!-- bof Quantity Discounts Contribution Example 4 Marketing Text -->
<?php
  $value = "ot_quantity_discount.php"; 
  include_once(zen_get_file_directory(DIR_WS_LANGUAGES . $_SESSION['language'] . 
          '/modules/order_total/', $value, 'false'));
  include_once(DIR_WS_MODULES . "order_total/" . $value);
  $discount = new ot_quantity_discount();  
  if ($discount->check() > 0) {
     echo '<div class="content" id="discountPolicy4">'; 
     echo '<table bgcolor="#99CCFF" border="1"><tr><td>Quantity</td><td>Price</td></tr>'; 
     $priceinfo =  $discount->get_discounted_prices($_GET['products_id'], $current_category_id); 
     for ($i = 0; $i < sizeof($priceinfo); $i++) {
         echo '<tr><td>' . $priceinfo[$i]['level']; 
         if ($i == (sizeof($priceinfo) - 1)) {
            echo " + "; 
         } else { 
            echo " - ";
            echo $priceinfo[$i+1]['level'] - 1; 
         }
         echo "</td><td>" . $priceinfo[$i]['price'] .  "</td></tr>";
     }
     echo '</table>';
     echo '<br /><br /></div>'; 
  }
?>
<!-- eof Quantity Discounts Contribution -->

This would produce output looking like this:

Quantity Discounts Marketing Example 4 Output

Quantity	Price
10 - 19	$424.96
20 - 99	$399.96
100 +	$249.98

If you just wanted to print out the best price, you could do something like this:

Quantity Discounts Marketing Example 5 Code

<!-- bof Quantity Discounts Contribution Example 5 Marketing Text -->
<?php
  $value = "ot_quantity_discount.php"; 
  include_once(zen_get_file_directory(DIR_WS_LANGUAGES . $_SESSION['language'] . 
          '/modules/order_total/', $value, 'false'));
  include_once(DIR_WS_MODULES . "order_total/" . $value);
  $discount = new ot_quantity_discount();  
  if ($discount->check() > 0) { 
     echo '<div class="content" id="discountPolicy5" style="background: #999933; padding: 3px; width: 400px;">'; 
     $priceinfo =  $discount->get_discounted_prices($_GET['products_id'], $current_category_id); 
     $last = sizeof($priceinfo) - 1; 
     echo "Priced as low as " . $priceinfo[$last]['price'] . 
        " in quantities of " . $priceinfo[$last]['level'] . " or more."; 
     echo '<br /><br /></div>'; 
  }
?>
<!-- eof Quantity Discounts Contribution -->

This would produce output looking like this:

Quantity Discounts Marketing Example 5 Output

Priced as low as $249.98 in quantities of 100 or more.

The restrictions for example 4 also apply here.

Quantity Discounts Marketing Example 6 Code - Counting by Currency

Some of the examples above - examples 3 and 4 for instance, do not work well when using Counting by Currency. Here are is a modification to example 3 to show the effect of discounting by dollars spent.

<!-- bof Quantity Discounts Contribution Example 6 Marketing Text -->
<?php
  $value = "ot_quantity_discount.php"; 
  include_once(zen_get_file_directory(DIR_WS_LANGUAGES . $_SESSION['language'] . 
          '/modules/order_total/', $value, 'false'));
  include_once(DIR_WS_MODULES . "order_total/" . $value);
  $discount = new ot_quantity_discount();  
  if ($discount->check() > 0) {
     echo '<div class="content" id="discountPolicy3">'; 
     echo '<table border="1" bgcolor="#FFFF66"><tr><td>Amount Spent</td><td>Discount</td></tr>'; 
     $dislist = $discount->get_discount_parms();
     $raw_dislist = $discount->get_discount_parms(true);
     global $currencies; 
     for ($i = 0; $i < sizeof($dislist); $i++) {
         echo '<tr><td>' . $dislist[$i]['level']; 
         if ($i == (sizeof($dislist) - 1)) {
            echo " + "; 
         } else { 
            echo " - ";
            echo $currencies->display_price($raw_dislist[$i+1]['level'] - 0.01, 0); 
         }
         echo "</td><td>" . $dislist[$i]['discount'] .  "</td></tr>";
     }
     echo '</table>';
     echo '<br /></div>'; 
  }
?>
<!-- eof Quantity Discounts Contribution -->

This would produce output looking like this:

Quantity Discounts Marketing Example 6 Output

Amount Spent	Discount
$100.00 - $399.99	$10.00
$400.00 +	$20.00

Quantity Discounts Marketing Example 7 Code - Counting by Currency

To flip this around and not use currency ranges is straightforward.

<!-- bof Quantity Discounts Contribution Example 7 Marketing Text -->
<?php
  $value = "ot_quantity_discount.php"; 
  include_once(zen_get_file_directory(DIR_WS_LANGUAGES . $_SESSION['language'] . 
          '/modules/order_total/', $value, 'false'));
  include_once(DIR_WS_MODULES . "order_total/" . $value);
  $discount = new ot_quantity_discount();  
  if ($discount->check() > 0) {
     echo '<div class="content" id="discountPolicy3">'; 
     echo '<table border="1" bgcolor="#FFFF66"><tr><td>Amount Spent</td><td>Discount</td></tr>'; 
     $dislist = $discount->get_discount_parms();
     $raw_dislist = $discount->get_discount_parms(true);
     global $currencies; 
     for ($i = sizeof($dislist) - 1; $i ≥ 0; $i--) {
         echo '<tr><td>' . $dislist[$i]['level'] . ' +'; 
         echo "</td><td>" . $dislist[$i]['discount'] .  "</td></tr>";
     }
     echo '</table>';
     echo '<br /></div>'; 
  }
?>
<!-- eof Quantity Discounts Contribution -->

This would produce output looking like this:

Quantity Discounts Marketing Example 7 Output

Amount Spent	Discount
$400.00 +	$20.00
$100.00 +	$10.00

Notes:

Yes, there really are four ways of getting the quantity discount information out of the ot_quantity_discount object. To review, they are:
- $discount->get_html_policy() - gets a preformatted string (example 1)
- $discount->get_discount_info() - returns an array of strings (example 2)
- $discount->get_discount_parms() - returns an array of {range, discount} pairs (example 3)
- $discount->get_discounted_prices() - returns an array of {range, price} pairs (examples 4,5)
where $discount is an ot_quantity_discount object created using

$discount = new ot_quantity_discount();

If you have used the apply_special_category_discount() or apply_special_item_discount() exits, you should add text below the call to the get_*() method you use to describe these special cases. As a convenience, each of the get_* methods now takes a product and category id, so you can modify the get_* function you're using in ot_quantity_discount.php to be aware of your exit logic. Alternately, you may make these messages conditional in your template using the logic described in my conditional messages tip.

If you are also using the Discount Preview Extension, please be sure that the second and third statements above in your code are "include_once" and not "include" as they were formerly.

You may also put the marketing logic described above into tpl_product_info_display.php if you wish to advertise your discounts there. In the case of get_discounted_prices(), this is the only place where it would make sense.

Use get_discounted_prices() with caution - it only makes sense for Discount Units percentage and Discount Basis Total By Item.

Files

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

Earlier versions of Quantity Discounts included a customized copy of includes/classes/shopping_cart.php; this was removed in Quantity Discounts 1.2 because the customization which Quantity Discounts required was incorporated into the 1.3.5 Zen Cart core code. Thus, Quantity Discounts 1.2 and higher are only compatible with Zen Cart 1.3.5 and higher.

Major Versions

Version 1.10 - Quantity Discounts by dollars spent
Version 1.8 - Integration with Zen Cart 1.3.8.
Version 1.7 - Add per item discounts by currency amount.
Version 1.4 - Added add_extra_level_discount() feature.
Version 1.2 - Integration with Zen Cart 1.3.5. NOT COMPATIBLE with pre Zen Cart 1.3.5 releases.
Version 1.1 - User Exits
Version 1.0 - First Release; Standard linkages for product and category.

Bugs

Quantity Discounts versions prior to 1.8 require a patch to run under Zen Cart 1.3.8. Take this function and paste it right above the function calculate_deductions() in the file includes/modules/order_total/ot_quantity_discount.php. The latest versions include this patch, but if you haven't upgraded, you must manually apply the patch.
If your Zen Cart version is 1.3.0 (or higher) but less than 1.3.5, you may still run Quantity Discounts version 1.1, but not 1.2 or higher. If your Zen Cart version is less than 1.3.0, you must upgrade to a more recent version of Zen Cart in order to run Quantity Discounts.

FAQ

Q: I'm using Discount Basis Total by Category, or a category related user exit, like exclude_category() or apply_special_category_discount(), and it's not working!
A: This is the most common question of all. Please see the Category Issues page for solutions.

Q: How do I install this software?
A: If you've never installed a Zen Cart mod before, please read my Guide to Mod Installation on Zen Cart.

Q: I can't seem to get Quantity Discounts to work. What am I doing wrong?
A: Please check the following things:

Go to Admin->Modules->Order Total. Do you see Quantity Discounts? If not, then you haven't installed it. Follow the README.
If you do see it, the circle at the right hand end of the row for Quantity Discounts should be green. If it's not green, reinstall it.
Click on Quantity Discounts. The Level and Amount fields are all numeric. Do not use dollar or percent signs in these fields.
If you're using Discount Basis "Total By Category," see the previous FAQ question.
If you've used any of the exits, make a backup of your ot_quantity_discount.php file and re-install from scratch; then apply your changes one at a time to see where it breaks. The most common error I have seen in exits is using the assignment operator ("=") where an equivalence test ("==") was intended.
Remember that the "levels" (Discount Level 1, Discount Level 2, etc.) are numbers of items, not number of dollars spent (unless you configure counting method to be by currency).
Re-read my Guide to Mod Installation on Zen Cart.

Q: I want to use discount units 'currency per item' but I don't see it!
A: This feature was added in Quantity Discounts 1.7 and requires a database change. Please download version 1.7 (or better), and copy the files to your store. Then, in Admin->Modules->Order Total, press remove on Quantity Discounts, then press install. You will have to reconfigure Quantity Discounts with your desired settings at this point.

Q: How do I tell if my stock is organized into subcategories?
A: In the Admin page, go to Catalog -> Categories/Products, and click on the category you're not sure about. If the entries that appear on the next page have file folders to the left of their names, then these are subcategories. If the products are directly below these folders, then these folders are the parent folder numbers you will use for category inclusions, exclusions and special discounts. If what is below these subcategories is more subcategories, continue drilling down until you get to products, and then go back one level. This is the "parent" category you will need to use.

Q: Why is there a Quantity Discounts contribution in the first place?
A: Zen Cart has a number of intrinsic discounting mechanisms: coupons, specials, sales, group discounts, discounts via the products price manager, etc.
While each of these fills a need, some retailers have different discounting needs that cannot easily be met by any of these features. The Quantity Discounts contribution was designed to meet these needs.

Q: What is the Products Price Manager?
A: The Products Price Manager implements Zen Cart's native Quantity Discounting mechanism. Go to Admin->Catalog->Categories/Products, select a product, and press the green $ sign. You are now in Products Price Manager.

Q: Is the Quantity Discounts contribution related to the native Quantity Discounting feature in Products Price Manager?
A: No. The Quantity Discounts contribution has its own configuration (through Modules->Order Total) and database entries, and is completely separate from the Products Price Manager.

Q: What does the Quantity Discounts Contribution do that Zen Cart's native Quantity Discounting mechanism doesn't?
A: Installing the Quantity Discounts Contribution and trying it out is the best way to get an understanding of the differences. A partial list is:

Zen Cart's Quantity Discount feature	That Software Guy's Quantity Discount Contribution
Only allows per-product quantity discounts	Allows you to discount by item, by parent category or by all items in the cart; extension allow you to discount by top level category for shops that use subcategories; you may also discount by dollars spent
Must be configured for every product on which you want to offer quantity discounts	Quantity Discounts Contribution applies to all products (except those you specifically exempt)
Allows unlimited numbers of discount levels, but discounts must be individually configured on each product	Allows only five discount levels in the admin panel with the ability to add more in the setup() function; discounting is applied to all products except where specified
Changing behavior involves modifying core code	A number of extensions are available for the Quantity Discounts contribution to make it work the way you want for your business
Marketing text is fixed, automatically generated	Marketing text may be customized to your needs, but must be added manually
Discounting by items purchased only	Discounting by items purchased or by dollars spent

Q: What does the Quantity Discounts Contribution using counting by currency do that the Price Sensitive Discount doesn't?
A: Here's the list:

Extensive support for automatically created marketing text
Automatically created Zen Cart Promotional Page for your discounts
Support for including/excluding products/categories from the spend computation
Support for unlimited numbers of spend levels
It works with Discount Preview

Q: I have a table on my product info screen that looks like this (below). Is this the Quantity Discounts Contribution?

Qty Discounts Off Price
1 $240.00	2-4 $228.00	5-9 $216.00	10+ $204.00

A: No - this is the native Quantity Discounts mechanism. Go to Catalog->Categories/Products and find the product this that shows this table. Press the green $ to enter Products Price Manager, and delete these discounts; they are separate from (and will be applied in addition to) any discounts you configure in the Quantity Discounts Contribution.

The Quantity Discounts Contribution's help is different; examples are provided here.

Q: Why does the Quantity Discounts contribution not provide more discounting levels in the Admin Screen?
A: Having a fixed number of discounts in the Admin screen is a design consequence of the Order Total implementation. I thought five was a reasonable compromise. Remember that a limitless number of discount levels are available by calling the add_extra_level_discount() function in setup().

Q: Why are there user exits for customization? Why didn't you put this in the Admin panel?
A: There are an endless number of combinations and permutations of how people want discounting to work. Rather than design a complicated user interface to present all these options, I have provided a framework that anyone with at least a beginner's knowledge of PHP should be able to extend.

Q: I would like my discounts to show up in the shopping cart. Why don't they?
A: The way the Order Total modules work is that they show up at checkout time. However, if you require the discounts to show up in the shopping cart, you may wish to consider purchasing the Discount Preview module for $30.

Alternately, you can indicate that you have a quantity discount policy by adding to TEXT_INFORMATION in includes/languages/english/shopping_cart.php, and inform the user that the discounts will be calculated (and visible) at checkout time. Additionally, changing SUB_TITLE_SUB_TOTAL in the same file to something like 'Sub-Total BEFORE Discount' will emphasize the fact that a discount will be added at checkout time.

Q: I only want discounts applied to items in category 11. How do I do this?
A: Update the function exclude_category() in includes/modules/order_total/ot_quantity_discount.php as follows:

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

Q: I don't want discounts applied to items in category 7. How do I do this?
A: Update the function exclude_category() in includes/modules/order_total/ot_quantity_discount.php as follows:

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

Q: I want to double my regular discounts for category 9 if the customer buys 10 or more, and triple them if he buys 100 or more. How do I do this?
A: Update the function apply_special_category_discount() in includes/modules/order_total/ot_quantity_discount.php as follows:

    function apply_special_category_discount($category, $count, &$disc_amount) {
        switch($category) {
           case 9:
                if ($count > 100) {
                   $disc_amount = $disc_amount * 3;
                } else if ($count > 10) {
                   $disc_amount = $disc_amount * 2;
                }
                break; 
        }
    }

Q: I only want discounts applied to product numbers 17 and 19. How do I do this?
A: Update the function exclude_product() in includes/modules/order_total/ot_quantity_discount.php as follows:

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

Q: I want discounts applied to all products except products 12 and 13. How do I do this?
A: Update the function exclude_product() in includes/modules/order_total/ot_quantity_discount.php as follows:

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

Q: How can I present my discounting schedule on the product page?
A: Create your custom template if you haven't already done so. Then customize the file includes/templates/template_default/templates/tpl_product_info_display.php. Look at the examples in marketing. Add the one that fits your needs best to tpl_product_info_display.php; start by putting it after the product description (although the placement is a matter of personal taste).

Q: Why are there four ways of getting the discounting information - get_html_policy(), get_discount_info(), get_discount_parms() and get_discounted_prices()?
A: I was too nice to deprecate the first two. Everything can actually be derived from get_discount_parms(); the other functions exist simply as a convenience.

Q: Can you explain how sales tax works?
A: Yes. See this page.

Extensions

The following Quantity Discounts extensions are available:

Discount by top level category, not just parent category.
Provide discounts only to certain customer groups (or exclude certain customer groups from discounting).
~~Discount by dollars spent, not items purchased.~~ built in to Quantity Discounts 1.10
Provide special discounts for each group of <n> items.
Do not discount products that are on special.

I charge a fee of $30 for each of these extensions. Contact me for details.

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