Adding PayPal Express Payment Method to Our Shopping Cart System

We have developed our own shopping cart system, using PHP, and it is already running on brandsdiscounter.com. Currently the cart only serves "Cash on Delivery" orders. This project task is to add a "pay by PayPal" option where customers can choose (by clicking on a radio button) which payment method to use. The PayPal method we need to add is "PayPal Express". When the user fills in, complete, and submit information on the PayPal form, he must be redirected to the [login to view URL] script to for order registration functions. (The page redirection path should be set using a variable so that we have the option to change later) At checkout page, where users choose to pay cash-on-delivery or by PayPal, a text needs to show next to the PayPal option: "Your card will be charged $###". Where ### is the money amount converted to US Dollars (2 decimal digits). Conversion rate should be set by variable so that we can change later. The email address receiving the PayPal payment needs to be stored in a variable so that we can change later. Any work needs to be well documented showing where the new code, changes, additions are made and why. We need this information so that we can integrate the new code you made with our templates system. The checkout process contains 3 scripts: (Please find attached the source code along with screenshots) • [login to view URL]: This shows cart contents • [login to view URL]: This is where users (customers) fills in their details and choose payment method • [login to view URL]: This script runs after the form on [login to view URL] is submitted. It registers the order, send an email to customer and the website admin, and shows a thank you message I have developed these scripts by myself so if you need any explanation, I will be happy to help. Current website and scripts functionality must not be affected by what you do. No milestone payments will be release before end of project and testing the solution. Any bid higher than the maximum we have set for this project will be ignored immediately.