Once your shipping and tax issues taken into account, the next logical step for your e-commerce store is discount codes, as these need to be entered at the shopping basket stage. Going hand in hand with discount codes are voucher codes and referral discounts. In this article by Michael Peacock, you will learn:

• How to create a discount code system
  • How to offer different types of discounts
  • How to take the discount into account at the shopping basket stage
• How to sell voucher codes on your store
• How to offer discounts to customers who bring us referral business

Discount codes

Discount codes are a great way to both entice new customers into a store, and also to help retain customers with special discounts. The discount code should work by allowing the customer to enter a code, which will then be verified by the store, and then a discount will be applied to the order.

The following are discount options we may wish to have available in our store:

• A fixed amount deducted from the cost of the order
• A fixed percentage deducted from the cost of the order
• The shipping cost altered, either to free or to a lower amount
• Product-based discounts (although we won't cover this one in the article)

It may also be useful to take into account the cost of the customer's basket; after all if we have a $5 discount code, we probably wouldn't want that to apply for orders of $5 or lower, and may wish to apply a minimum order amount.

Discount codes data

When storing discount codes in the framework, we need to store and account for:

• The voucher code itself, so that we can check that the customer is entering a valid code
• Whether the voucher code is active, as we may wish to prepare some voucher codes, but not have them usable until a certain time, or we may wish to discontinue a code
• A minimum value for the customer's basket, either as an incentive for the customer to purchase more or to prevent loss-making situations (for example a $10 discount on a $5 purchase!)
• The type of discount:
  • Percentage: To indicate that the discount amount is a percentage to be removed from the cost
  • Fixed amount deducted: To indicate that the discount amount is a fixed amount to be removed from the order total
  • Fixed amount set to shipping: To indicate that the discount amount is to be the new value for the shipping cost
• Discount amount; that is, the amount of discount to be applied
• The number of vouchers issued, if we wish to limit the number of uses of a particular voucher code
• An expiry date, so that if we wish to have the voucher code expire, codes with a date after the stored expiry date would no longer work

Discount codes database

The following table illustrates this information as database fields within a table:

The default value for num_vouchers is -1, which we will use for vouchers that are not limited to a set number of issues.

The following code represents this data in our database:

CREATE TABLE `discount_codes` (
`ID` INT( 11 ) NOT NULL AUTO_INCREMENT ,
`vouchercode` VARCHAR( 25 ) NOT NULL ,
`active` TINYINT( 1 ) NOT NULL ,
`min_basket_cost` FLOAT NOT NULL ,
`discount_operation` ENUM( '-', '%', 's' ) NOT NULL ,
`discount_amount` FLOAT NOT NULL ,
`num_vouchers` INT( 11 ) NOT NULL DEFAULT '-1',
`expiry` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ,
PRIMARY KEY ( `ID` )
) ENGINE = INNODB DEFAULT CHARSET = latin1 AUTO_INCREMENT =1;