Website back-end integration

We are creating an instructor led and self paced training website. We already have a vendor engaged in creating the designs of the website in HTML5, Javascript. So there is no requirement for designing the web pages. However, we need the pages to populate content from the back-end tables (MySQL). We want a fully functional Shopping Cart using Paymentech gateway. So the freelancer selected MUST MUST MUST have experience on coding for Shopping carts integrated with payment gateway for credit card and paypal payments. Another requirement is to allow students to register online, view their registered courses and their course schedules and other course details. The backend tables will store information for all course offerings, schedules, rates (cost) of courses, payment options etc. The requirements include sending emails containing embedded HTML i.e., registration/ payment confirmation emails, emails for reminder on scheduled classes and informative emails for marketing of courses. An admin option to add/delete/ update course offerings (title, description of course, prerequisites, cost, schedule etc). Further, there will be a collaboration feature for student community so that students may be able to communicate between themselves, post comments, share files. THIS IS NOT AN LMS system. We expect code that is protected from robot spam, SQL injection and DDOS attacks. Deprecated PHP code will not be acceptable. ONLY EXPERIENCED WEB BACKEND DESIGNERS and DEVELOPERS MAY APPLY. WE WILL LOOK FOR PROOF OF PAST EXPERIENCE AND REFERENCES.