article selling site management script

I need to create a script for managing a site selling items Articles are all in text format (TXT) My staff realizes, for example, 50 different articles on marketing, and then puts them in the appropriate category Then creates 50 other articles on SEO techniques, puts them in the appropriate category, and so on The customer must be able to enter the site, and choose a category from which pick one or more 'articles of interest, which can be downloaded by clicking on it From that moment that article should not be more 'downloaded by other users, and disappear from the list of items available Every single item will cost, and the customer must be able to download only the number of articles which have paid in advance, for example, Paypal Example: an item cost $ 1, the customer can 'buy minimum 5 to total $ 5. Pay with Paypal and enter the download, will be entitled to download 5 articles. Its purchase should not have expiration, or may access the download until they have downloaded as paid. The customer must be able to have a control panel where can check how many and which articles had previously purchased and downloaded, with the ability to download them again if lost or incorrectly download It must also be made for an area Administrator, where you can: - Check the data users and their status downloading - Send an email to individual users or a general email - Bannare or inhibit access to fraudulent users - Set the number of downloads available for each user and the cost per article The application will be preferably in PHP and run on Linux servers, with 11 Cpanel and mysql