Add the desired variations to the customer’s cart. That’s it.

$cart->add([
  'id' => 'nice-shoes',
  'key' => 'nice-shoes-abc',
  'color' => 'red',
  'size' => 38,
]);

You can even set a custom price within the add method:

$cart->add([
  'id' => 'nice-shoes',
  'key' => 'nice-shoes-xyc',
  'color' => 'gold',
  'size' => 41.5,
  'price' => 249.99,
]);

Tax is calculated automatically based on the tax value defined in the product page.

If you add the same product to the cart, the cart item will be merged/overwritten by default (the quantity is added up). To add more than one variant of a product to the cart, you have to set a unique key for each variant.

If you want to combine product variations with stock management things are getting more complicated. We recommend to think of product variations as own products.

content/nice-shoes/variant-red-41/product.txt

Title: Nice shoes
----
Price: 99.99
----
Tax: 19
----
Color: red
----
Size: 41
----
Stock: 10

content/nice-shoes/variant-red-40/product.txt

Title: Nice shoes
----
Price: 99.99
----
Tax: 19
----
Color: red
----
Size: 40
----
Stock: 8

content/nice-shoes/variant-gold-40/product.txt

Title: Nice shoes
----
Price: 249.99
----
Tax: 19
----
Color: gold
----
Size: 41
----
Stock: 1

Add variant to cart

$cart->add([
  'id' => 'nice-shoes/variant-gold-40',
]);