Web development - codeigniter work done

I am trying to do a online food ordering website for a client of mine and am doing it using tastyigniter which is using codeigniter framework. I need to do something like chained/dependent options that show and hide based on the pizza size selected.

For example if I select a 10" pizza, the extra topping prices need to be £0.70 or if I select a 13" pizza size, the extra topping prices will be £0.80 so basically the extra topping prices vary based on what pizza size is selected and so if the 10" pizza size is selected then the extra topping options/prices will show £0.70 and not the £0.80

Hope that makes sense

The site so far is https://www.broadwaymediadesigns.co.uk/sites/fastfoodparadise/local?location_id=11