PHP User Sign-up, Login & Password, Integrated with PayPal's

We require the following: 1)a customer sign up page where the customer is able to create a user name and password, they must also provide firstname,lastname,& email address- this data will be added to existing database on our server. 2) a user login page that checks to see the userlevel associated with the customer in the database. If the cutomer is above a given level they have access to a special download page where they can download files (pdf, word, excell). There must be a mechinism that stops unwanted downloads from occuring. Only customers with the correct user level should have access to the download area. Note: This area requires a login and is not a secret link, but rather a logic test base access method. 3)a purchase page with a button that is a direct link to paypal, upon clicking and completing transaction, the page will verify via paypal's IPN device. If the payment is verified the userlevel in the database is increase to proper level and user is taken to a thankyou page and is required to login. If failure, they are taken to a failure page. A user that signs up but does not make a purchase: userlevel = 0 To make a purchase a user must sign up. When a user makes a successful purchase: userlevel = 1