Using an external API for fetching item and inventory data

Due to how our pricing model works we have an application built already that handles all of our inventory needs (we use a declining price model so prices change daily). We would like to be able to integrate this with phpPOS, so that when we scan an item in the checkout screen that it will make a call to our inventory system to pull price and product information. I am having a little bit of trouble getting this working so that it does not use the local database.