Question

I’m working on a site that will create pre-set packages of items. To start, I’m using Amazon to test the idea, pulling some affiliate sales, and then I’ll fulfill orders myself if the idea deems successful.

My goal is to have a "buy now" type button, and upon clicking, the user will arrive at an Amazon checkout now page, with a cart pre-filled with items of my choosing, and my affiliate number.

I’m a PHP developer, so if a solution must be language specific, that’s the language to go with. If it’s more of a conceptual answer, or if there’s an API for this, that works too.

Answer 1

You may use link that contains ASINs and their quantity. It doesn’t add items to someone’s cart but confirms to add to cart.

URL:
http://www.amazon.com/gp/aws/cart/add.html

Parameters:
- AssociateTag
- ASIN.<number>        <number> starts at 1
- Quantity.<number>    one quantity parameter for each ASIN parameter

Example (parameters separated by line break for visibility):
http://www.amazon.com/gp/aws/cart/add.html
    ?AssociateTag=your-tag
    &ASIN.1=B003IXYJYO
    &Quantity.1=2
    &ASIN.2=B0002KR8J4
    &Quantity.2=1
    &ASIN.3=B0002ZP18E
    &Quantity.3=1
    &ASIN.4=B0002ZP3ZA
    &Quantity.4=2

One line example: https://www.amazon.com/gp/aws/cart/add.html?AssociateTag=your-tag&ASIN.1=B003IXYJYO&Quantity.1=2&ASIN.2=B0002KR8J4&Quantity.2=1&ASIN.3=B0002ZP18E&Quantity.3=1&ASIN.4=B0002ZP3ZA&Quantity.4=2&ASIN.5=B004J2JG6O&Quantity.5=1

ASINs are found in the product’s page URL or by searching for “ASIN” on the product page. More details here