I am developing a website that sells design and print items. My print items run on a formula that needs me to be able to have one price modifier such as "paper type" affect the final price depending on what the "dimensions" modifier is.

To be clear my price modifiers need to affect each other's price.

Is this possible with Expresso Store. If so, what are the solutions?

  • Are you using Store currently? Have you tried using the current modifiers system to do this? Also, could you provide an example of the pricing you are trying to achieve? Jan 19, 2013 at 9:50
  • Hi Adrian, I am using the store currently. It seems that the store is more "one-dimesional". Each price modifier adds or subtracts from the final price, but the modifiers don't affect each other. Jan 22, 2013 at 21:41
  • I would love to add an example, but the site is kind of "hidden" from the public during its development stage. Jan 22, 2013 at 21:42
  • Ok. I meant just write down an example product with the various pricing options, so we can see how you want the prices to interact. Jan 22, 2013 at 23:55

1 Answer 1


There isn't any way to customize how the price modifiers work. Generally modifiers can only add or subtract the price, not multiply or use any other formula (because is leads to issues in which order the modifiers are applied, among other reasons).

Often the solution to this is to simply "flatten" your modifiers into a single select/radio menu, for example:

  • Paper (10 x 10) - $1
  • Paper (10 x 10) - $2
  • Cardboard (10 x 10) - $5
  • Cardboard (20 x 20) - $20

Another option would be to write a PHP extension using the store_cart_item_update_end hook, which allows you to change the price of items in the cart based on any criteria you need (for example, you can let users enter custom dimensions, then change the price of the item based on the dimensions entered).

  • Thanks Adrian, can you give me a link to any documentation on store_cart_item_update. Any extra info would be great. Jan 23, 2013 at 6:07
  • There is a good guide on extension development here. Just use our extension hooks in the same way. To tell what the hook does, you really need to look at the code in store_cart.php. You can also use print_r($item) inside the hook to see which variables are abailable to you. Jan 23, 2013 at 7:06
  • Hey, Just wanted to check up again on this. I am having a hard time figuring out how to add this extension you are talking about. Also, how does writing this extension affect the javascript that runs the automatic price updater? Feb 2, 2013 at 18:18
  • Did you follow the extension development tutorial I linked to? The cart extension hook won't affect the javascript at all - you will have to come up with your own javascript if you want automatically updating prices on the product page as well. Feb 3, 2013 at 2:35

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