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Table Discounts

A Zen Cart™ discounting module for bulk purchases.

Zen Cart has a built-in quantity discounting mechanism (native quantity discounts), which allows you to discount bulk purchases of a single item. There is also my Zen Cart Quantity Discount Module, which allows you to discount bulk purchases of multiple items, grouped by product id, category id or dollars spent. However, there is no easy way to have different discount schedules for different categories, or to link multiple categories together for discounting. For example, suppose you had one discount schedule for category 7, and a completely different discount schedule for category 9. The solutions I suggested in the past were:

Simply clone the Quantity Discounts contribution and set up the second discount schedule in the clone.
Use Big Chooser, which permits Quantity Discounting

Obviously the first method doesn't scale well. The second method works, but since Big Chooser is designed to do "Buy <some items>, get a discount on <some other items>", it requires a pretty hairy (if I do say so) amount of configuration when you want to discount the entire group of items under consideration. That's why I created Table Discounts.

Background: See the Zen Cart Matrix-o-discounts

Relevance: Zen Cart™ 1.3.5 and forward

Cost: $60 Buy Now!

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

Promotional Page Download: free from my website (you must buy Table Discounts separately)

Current Version: 1.1b

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.

FAQ: click here

Installation: click here

Marketing Text: click here

Add-Ons:
Table Discounts is an order total module, so the discount is not visible until the second page of checkout. If you want to see the discount on the shopping cart page (or sidebox), look at Discount Preview.

Overview:

Table Discounts permits a shop to create table based discounts, grouping products by category, id or manufacturer, and discount purchase levels by percent, a dollar amount per unit, or a flat dollar amount. The number of discounts supported is unlimited.

The discounts themselves are not entered into an admin panel; they are specified by modifying the setup() function in the file includes/modules/order_total/ot_table_discounts.php.

Table Discounts is configured by specifying lists of items which are eligible for discounting and then specifying the levels at which discounts occur.

Table Discounts requires you to add these conditions and parameters to the module itself - they are not configured through the admin panel. This sounds complicated, but it's not that bad, and many examples of common discounting practices are provided. Please note that Table Discounts only provides a discount; it does not automatically add items to the cart.

The calling conventions for building a table discount are as follows:

You begin with a text string that describes the discount. So suppose the discount was, "Buy 4 items from Category 3, save 10%. Buy 8 items, save 20%."

Edit includes/modules/order_total/ot_table_discounts.php, and go to the bottom where the setup() function is located. Change it to:

function setup() { 
   $this->add_table("Bulk discounts on category 3");
     $this->set_constraint(CAT, 3);
     $this->set_discount("%", 4, 10, 8, 20);  
}

The statements "set_discount" and "set_constraint" are called parameter statements. Parameter statements apply to the add_table statement they immediately follow. I have provided a visual cue for this by indenting the parameter statements on this page by three spaces. The following types of parameter statements are currently supported:

set_constraint - specifies the items which are eligible for this discount
set_discount - specifies the table discount
set_support - provide additional information on the discount
set_group - only apply this discount to members of the listed groups
set_constraint_regprice - specifies that items counted towards the constraints must not be on sale or special
set_count - indicates that either tiering or case discounts should be used
set_policy_lowtohigh - When constraints other than PROD are used, the list of products is processed from highest price to lowest price by default; this command inverts that behavior

A Note on Taxes

The way taxes are handled internally in Zen Cart 1.x is that the entire tax amount is stored in the cart; the tax is not broken down on an item by item basis. For this reason, tax recalculation after discounting may not work perfectly if items which attract different levels of tax are in the cart - for example, taxable and non-taxable items. This issue is discussed in this forum post, and we are hopeful that Zen Cart 2.x will solve this problem.

Included Taxes and My Mods

This section is only relevant to Zen Carts which use "Display Prices with Tax" = true (in Admin->Configuration->My Store).

If your shop displays prices with tax included, you should configure my discounting mods to use Include Tax = true and set Re-Calculate tax to either "Standard" or "VAT" (depending on how taxes are handled in your jurisdiction).

There was a time when my software would gross up percentage discounts for tax but not currency based discounts. I decided to change this and handle both uniformly, so now (post April 2010) if you configure one of my discount mods to use include taxes = true, your discount will be grossed up whether it is a currency value or a percentage.

Detailed Description:

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

This is where the tax settings and sort order are configured.

Once this is done, the file includes/modules/order_total/ot_table_discounts.php. is edited to specify the discounts themselves. The discounts are specified according to the following syntax:
```
function setup() {
$this->add_table(<description >); 
  $this->set_constraint(<discount basis 1>, <id 1> ...  <discount basis n>, <id n>); 
  $this->set_discount(<discount units>, <min quantity 1>, <discount 1>, ... <min quantity n>, <discount n>); 
}
```
Where:
"discount basis" is one of PROD, CAT or MANUF
"id" is the product, category or manufacturer id
"discount units" is one "%", "$" or "$$"
(% meaning percent off, $ meaning dollars off per item, $$ meaning an absolute dollar discount off)

(Note: your local currency is used if dollars are not your default currency)
The set_discount and set_constraint commands apply to the add_table command they immediately follow.

So for example,
```
$this->add_table("Quantity discounts on category-5 items");
  $this->set_constraint(CAT, 5);
  $this->set_discount("$", 50, 2, 100, 5);
```
would mean "Buy 50-99 category 5 items, get $2 off each, buy 100 or more, get $5 off each."
```
$this->add_table("Bulk discounts on product-7");
  $this->set_constraint(PROD, 7);
  $this->set_discount("$$", 10, 5, 20, 12);
```
would mean "Buy 10-19 of product 7, get $5 off your purchase, buy 20 or more, get $12 off."
```
$this->add_table("Buy multiple items from manufacturer 8 and save!");
  $this->set_constraint(MANUF, 8);
  $this->set_discount("%", 100, 5, 200, 12);
```
would mean "Buy 100-199 of products from manufacturer 8, get 5% off, buy 200 or more, get 12% off."

The category used in Table Discounts may be the category id at any level, not just the parent category.
```
Men's Clothing (category 3)
     |
     ---->  Shirts (category 7)
            |
            -------> shirt A     
                     shirt B
                     shirt C 
     ---->  Shoes (category 8)
            |
            -------> shoe A     
                     shoe B
                     shoe C 
     ---->  Hats (category 9)
            |
            -------> hat A     
                     hat B
                     hat C 
```
In this example, if category 7 were specified, only the shirts would be considered for discounting. If category 3 were specified, shirts, shoes and hats would be considered for discounting. This is different from Quantity Discounts, which only permits parent categories to be used.

What is also different from Quantity Discounts is the ability to specify multiple categories. To discount Shoes and Shirts, mix and match buying 3 get 10% off, you can do
```
$this->add_table("Mix and match shoes and shirts at a discount");
  $this->set_constraint(CAT, 7, CAT, 8);
  $this->set_discount("%", 3, 10);
```
To have buy 3 get 10% off, buy 6 get 20% off, buy 12, get 30% off, you simply expand the set_discount command.
```
$this->add_table("Mix and match shoes and shirts at a discount");
  $this->set_constraint(CAT, 7, CAT, 8);
  $this->set_discount("%", 3, 10, 6, 20, 12, 30);
```
Applying the maximum discount to all items once the final threshold has been crossed is the type of discounting most retailers want to offer. But there are two other modes of discounting which can be done with table discounts: tiered discounting and case discounting.

Checkout Page User Interface
Table 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:

Tiered discounting and Case discounting

First, an explanation of terminology.

Tiered discounting discounts items with by applying specific discounts to specific counts of products within a single order. If you want one price for the first 10 items, another for the next 20 and another for the next 50, look at tiered discounts.
Case discounting only discounts groups of items in specific numeric quantities. If you want to offer special prices for groups of 6, 12 and 24, but no special prices for other multiples, look at case discounting.

Tiered discounts were added to Table Discounts in version 1.1. Here are some examples of how they can be used.

Suppose your discount was:

function setup() {
       $this->add_table("Discount on hardware"); 
          $this->set_constraint(CAT, 1);
          $this->set_discount("%", 20, 10, 50, 20, 100, 25);
}

This corresponds to the following discount:

20 - 49	10%
50 - 99	20%
100 +	25%

But suppose your pricing is "tiered," so that the better prices are only available for the items that exceed that tier's quantities.

If you bought 100 items for $10 each, the regular (non-tiered) discount would be $100 * 25%, which would be $250.00.

With tiering, the discounting would be as follows:

19 at 0% off

30 at 10% off = $30

50 at $20% off = $100

1 at 25% off = $2.50

for a total discount of $132.50.

To add tiering, simply add the statement set_count(BY_TIER) to your discount. So the new setup() function would be:

function setup() {
       $this->add_table("Discount on hardware"); 
          $this->set_constraint(CAT, 1);
          $this->set_discount("%", 20, 10, 50, 20, 100, 25);
          $this->set_count(BY_TIER); 
}

Suppose instead of 100 $10 items, there was a mix of items. If there are 49 $10 items and 51 $20 items, the tiered discount is (applied highest to lowest) is:

19 $20 items at 0% off $0

30 $20 items at 10% off = $60

2 $20 items at 20% off = $8

48 $10 items at 20% off = $96

1 $10 item at 25% off = $2.50

for a total discount of $166.50.

Some vendors will not want to discount highest to lowest because it means the lowest priced item will attract the greatest discount, which could be confusing or disappointing to customers.

To discount lowest to highest instead, use the command

$this->set_policy_lowtohigh();

If the discount was applied lowest to highest, you would have the setup function being:

function setup() {
       $this->set_policy_lowtohigh(); 
       $this->add_table("Discount on hardware"); 
          $this->set_constraint(CAT, 1);
          $this->set_discount("%", 20, 10, 50, 20, 100, 25);
          $this->set_count(BY_TIER); 
}

and the discounts being:

19 $10 items at 0% off

30 $10 items at 10% off = $30

50 $20 items at 20% off = $200

1 $20 item at 25% off = $5.00

for a total discount of $235.

Note that set_policy_lowtohigh() applies to *all* table discounts; it is a global setting.

Another counting option is provided: by case. For instance, suppose your product was available in cases of 35, with a 10% case discount, but with quantities less than a full case at no discount.

function setup() {
       $this->add_table("Case discount on item 25"); 
          $this->set_constraint(PROD, 25);
          $this->set_discount("%", 35, 10); 
          $this->set_count(BY_CASE); 
}

This would produce the following table:

10%

If you bought 100 items for $10 each, the case discount would be as follows:

30 at 0% off

2 cases (70) at 10% off = $70

for a total of $70 off.

If the discount was $10 per case rather than 10% per item in the case, you could use "$$" discounting, i.e.

function setup() {
       $this->add_table("Case discount on item 25"); 
          $this->set_constraint(PROD, 25);
          $this->set_discount("$$", 35, 10); 
          $this->set_count(BY_CASE); 
}

Note that using "$" instead of "$$"

          $this->set_discount("$", 35, 10);

would discount $10 per item, rather than $10 per case.

Installation Instructions:

Back up everything! Try this in a test environment prior to installing it on a live shop.
If you already have the Table Discounts module installed, please deinstall your old copy by going to Admin->Modules->Order Total, selecting "Table 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 'Table Discount' listed along with all the other modules available.
Click on 'Table 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 "Table 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 Table Discounts Promotional Page by following the links at the top of this page.

More Examples

You can use Table Discounts to create a segmented group discount. For example, suppose you want to offer a 10% discount off 3 or more category 7 and 8 to customers in one group only.

Create the group in Admin->Customers->Group Pricing, but set the discount amount to 0%. This way, Group Pricing won't do additional discounting for all products. Suppose the group number was 2. Use the "set_group" statement to only allow the discount to group 2 members:

$this->add_table("Mix and match shoes and shirts at a discount");
  $this->set_constraint(CAT, 7, CAT, 8);
  $this->set_discount("%", 3, 10);
  $this->set_group(2);

If you wanted to do a 100% discount on category 7 items for group 2 and a 50% discount for group 3, you would code:

$this->add_table("100% off category 7 items for group 2");
  $this->set_constraint(CAT, 7); 
  $this->set_discount("%", 1, 100);
  $this->set_group(2);

$this->add_table("50% off category 7 items for group 3");
  $this->set_constraint(CAT, 7); 
  $this->set_discount("%", 1, 50);
  $this->set_group(3);

To discount 10% for group 5 on categories 1-4, you would do

$this->add_table("10% off category 1-4 items for group 5");
  $this->set_constraint(CAT, 1, CAT, 2, CAT, 3, CAT, 4); 
  $this->set_discount("%", 1, 10);
  $this->set_group(5);

If you have two products, 230 and 231, that you want to give 10% off for mix and match quantites of 100 or more:

this->add_table("Bulk discounts on product 230 and 231");
  $this->set_constraint(PROD, 230, PROD, 231);
    $this->set_discount("%", 100, 10);

Marketing

What good is having cross selling and upselling specials if you don't advertise them?

Table Discounts may be automatically displayed in two places: on the product info page, and on a separate promotional page. We'll talk about the product info page first.

Customize the tpl_product_info_display.php file to advertise your discounts. Copy the file

includes/templates/template_default/templates/tpl_product_info_display.php

into

includes/templates/<Your Template>/templates

Then add this block of code to the new copy of tpl_product_info_display.php:

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

The placement of this code is a matter of personal preference; try placing it below the product description and adjust to your tastes. It creates a message on your page that advertises the discounts that are applicable to that product.

For example, the following discount

    function  setup() {
       $this->add_table("Discount on movies"); 
          $this->set_constraint(CAT, 46);
          $this->set_discount("%", 5, 3, 10, 5, 20, 8);
    }

would generate this image:
Table Discounts Marketing

The following discount

    function  setup() {
       $this->add_table("Discount on movies"); 
          $this->set_constraint(CAT, 46);
          $this->set_discount("$", 5, 3, 10, 5, 20, 8);
    }

would generate this image:
Table Discounts Marketing

If you would like to have a Table Discounts Promotional Page that describes your store's table discounts as part of your categories sidebox, you may download a copy here.

Files

(new) includes/languages/english/modules/order_total/ot_table_discounts.php
(new) includes/modules/order_total/ot_table_discounts.php
(new) includes/templates/custom/templates/tpl_table_discounts_marketing.php

Formal Syntax of Tables and Parameters

Tables and Parameters, which are specified in the setup() function of ot_table_discounts.php, are the mechanism for configuring a store's discounts.

Tables

Discounts always begin by specifying a table. All subsequent parameters (until the next table) apply to this table.

$this->add_table(<description>);

where:

description

Is a textual description of the discount. This description is not automatically created the way it is in Better Together or Combination Discounts; it must be added manually. The reason for this is to allow greater flexibility

Parameters - set_constraint

The set_constraint() command specifies the items to which this discount applies.

$this->set_constraint(<required_purchase_quantity 1>[,<required_purchase_quantity 2>,...,<required_purchase_quantity n>]);

where: Note that unlike in Big Chooser, quantities are not specified in the set_constraint parameter in Table Discounts; they are specified in the set_discount parameter.

required_purchase_quantity

is the string PROD, CAT, or MANUF, followed by an identifier (product or category id, or manufacturer id)

Parameters - set_discount

The set_discount() command specifies the items or categories whose prices should be reduced if the condition has been met.

$this->set_discount(<discount units>, <discount 1>[,<discount 2>,...,<discount n>]);

where:

discount_units	is the string "%", "$" or "$$", meaning percent off, dollars off per quantity purchased, or flat dollars off.
discount	is the string PROD, CAT, MANUF, followed by an identifier (product or category id, or manufacturer id), followed by a quantity, followed by a percent or dollar sign, followed by an amount <PROD \| CAT \| MANUF> <product, category or manufacturer identifier>

Parameters - set_support

The set_support() command provides additional supporting text to describe your promotion. It is completely optional.

$this->set_support(<text>);

where:

text	is a text string, which can be plain text or a link

These strings are displayed on your promotional page, and optionally, on your product info page if you customize the file includes/templates/YOUR_TEMPLATE/templates/tpl_table_discounts_marketing.php

Parameters - set_group

The set_group() command specifies that the discount is only available to members of the listed group(s).

$this->set_group(<group 1>[,<group 2>,...,<group n>]);

where:

group

is the group eligible to receive the discount

Parameters - set_constraint_regprice

Require items counted towards the constraint not be on sale or special.

$this->set_constraint_regprice();

Parameters - set_policy_lowtohigh

Normally the list of products meeting the constraints for a discount is processed from highest price to lowest price by default; this command inverts that behavior. This becomes important in tiered and case discounting. For more information on this discounting model, please see tiered discounting and case discounting.

$this->set_policy_lowtohigh();

The set_policy_lowtohigh command was added in version 1.1.

Parameters - set_count

The set_count command allows you to specify case or tiered pricing for your discount. For more information on this discounting model, please see tiered discounting and case discounting.

$this->set_count(BY_TIER|BY_CASE);

The set_count command was added in version 1.1.

Major Versions

Version 1.1b - 08/20/2010 - Correction in marketing text.
Version 1.1 - 06/04/2010 - Tiered and case discounts.
Version 1.0.1 - 04/01/2010 - First Release; Standard linkages for product and category.

FAQ

Q: I'm using a category based discount and it's not working!
A: 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 Table Discounts to work. What am I doing wrong?
A: Please check the following things:

Go to Admin->Modules->Order Total. Do you see Table 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 Table Discounts should be green. If it's not green, reinstall it.
If you're using category discounts, see the previous FAQ question.
Re-read my Guide to Mod Installation on Zen Cart.

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.

Q: Why is there a Table 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 Table Discounts contribution was designed to meet these needs.

My Zen Cart Quantity Discount Module, allows you to create a single table discount. My Zen Cart Big Chooser Module, allows you to create table discounts, but with a very verbose, tedious syntax, since the real intention of Big Chooser is to create "Buy these items, get a discount on those other items" type discounts. So I mixed the two to create Table Discounts.

Q: How do I find out the manufacturer id so I can use MANUF?
A: See Manufacturers in Zen Cart for some techniques.

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 Table Discounts contribution related to the native Quantity Discounting feature in Products Price Manager?
A: No. The Table Discounts contribution has its own configuration (through the setup function), and is completely separate from the Products Price Manager.

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

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

Q: Why didn't you put all the configuration for Table Discounts 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 table 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.

Extensions

The following Table Discounts extensions are available:

Show Table Discounts on the shopping cart page using Discount Preview
Market your Table Discounts using the Table Discounts Promotional Page (this one's free).
Other customizations as required: include and exclude items, offer discounts to certain groups only, etc.

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

I charge a fee of $60 for Table Discounts. The fee covers software only; installation is extra if you require help.

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