an online store with paypal express checkout

Please note that the operation of this online store is different from what we commonly see on the Internet. The basic functions of this site are as follow - index page -> just need to include user login-logout/register button -> loged-in member area -User Register ->User name,password,email,shipping address,[phone no. (optional to the user).] -User Login ->upload .stl file with its descriptions e.g. name,color,actual size of the 3D model ->price for printing that .stl file can be varying(mainly depends on its actual size). please indicate the location of the formula in the code so i can change it later.(while developing, u can use any formula for testing) ->shopping cart, files(as the products to be checkout) should be selected from where the user uploads the .stl files (user's own list of uploads). ->when user selects a .stl file(to be printed by me), price is calculated. ->user than checkout by using paypal express checkout api (use your own api usr id,pw,signature for testing) ->after the payment has confirmed, an invoice (which contains the user id , .stl file id, stl 3D model color,size) is sent to my admin page. -User settings ->user can change their pw,email and address. ->user can detele their uploaded files. - Admin panel ->list of invoices ----> details of the 3D object to be printed ->contact info of the user e.g. Shipping address , phone no. , email. The system should be secure and maintainable . Try to keep the codes simple and tidy with function description. *************************************************************** ***Try to use html,javascript,php,mySQL if possible.*** *************************************************************** If possible, use simple UI framework like bootstrap Detailed Styling ,graphic/UI design is not necessary . :)