Paypal Shopping Cart

PayPal's documentation has really very subtle hints about what needs to be done to get Paypal working for a website, and you need to plough through a lot of links to figure out anything useful.

On sign up, they take the user to a page with customizable buttons for Buy Now, Subscribe, Shopping Cart. Now, if the site has only one item to sell, it should use the 'Buy Now', if it is selling subscriptions, use the Subscription Button. For a site that sells multiple items and needs a shopping cart, Paypal has tied up with some Shopping Cart providers.

There is however an option of creating your own light weight shopping carts. Its called Third Party Shopping Cart. This is especially useful when a website is just starting out and it doesn't need the whole armada of a formal Shopping Cart, but it needs something beyond a Buy Now or Subscription Button.

To create your own shopping cart, we need to have a list of items, quantities and price. Then we pass it to Paypal as follows:

<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
    <input type="hidden" name="cmd" value="_cart">
   <input type="hidden" name="upload" value="1">
   <input type="hidden" name="business" value="seller@mywebsite.com">
   <input type="hidden" name="item_name_1" value="Item Name 1">
   <input type="hidden" name="amount_1" value="1.00">
   <input type="hidden" name="quantity_1" value="2">
   <input type="hidden" name="shipping_1" value="1.75">
   <input type="hidden" name="item_name_2" value="Item Name 2">
   <input type="hidden" name="amount_2" value="2.00">
   <input type="hidden" name="quantity_2" value="3">
   <input type="hidden" name="shipping_2" value="2.50">
   <input type="submit" value="PayPal">
</form>

The suscript-ing numbers item_name_1, amount_1 all refer to the first item on list. There are other options like tax_x, handling_x, discount_amount_x, weight_x. The value of x must increase by 1 for each new item in the cart.

There are some options that can be applied to the entire cart like: currency can be specified with hidden currency, units of weight can be given as weight_unit, tax can be calculated for the entire cart instead of per-item by using tax_cart, discount_amount_cart to charge a single discount amount for the entire cart, discount_rate_cart to give a discount percentage for the entire cart.

This will display a PalPal button on the site. Clicking on that button takes the user to PayPal's site where it shows the list of all the items purchased and the total quantity, and invites the user to pay using the PayPal account or a credit card.

To make Paypal really integrate with a website though, the website needs IPN or PDT.  Stackoverflow has a good discussion on which one to use. We use IPN and are happy with it so far.