This payment page is similar to the simple checkout process with the added option of choosing the addon(s). Once you create the product and add the plans, you can create the addon(s) and choose the plan they should be associated to.
To display the addon(s) after the plan is chosen, all you have to do is add the addon parameters along with the plan URL. Accordingly, the addon(s) will be displayed once the plan is selected. Learn more
