Add & Edit toppings to pizza/product

We have a live site ([login to view URL]) built with php, mysql and some javascript. The site offers list of restaurants who offers delivery and takeaway services. Each restaurant has its product list, these products are saved in a mysql database table. In products page, when a customer clicks "Add to basket" the product is added to the order table of database. Before the point of "Add to basket" we need to add codes which will make it possible to add extra topping(s) to the product in menu. To add extra topping(s), each restaurant needs to have its own list of toppings and each topping needs to have 2 or 3 price options, depending on for example, if the customer is ordering a small, medium or large pizza. The website's scripts origin is [login to view URL] If you need more information, please let me know.