Web Based File Management

The aim is to build a service which allows visitors to store their files online, similar to Yahoo Briefcase, and also allow visitors to host simple websites. The service will be free, and will use leftover space on our hosting account, of which their is plently. The system will basically be a file manager system, which we want to be easy to use and must be able to do the following:- User Registration - Collect Username, Password and additional information from visitor - Make a folder on the server with the same name as the username, if it has not already been taken, or ask for another name if unavailable. - Send a welcome e-mail to the user. - Send an e-mail to the administrator informing of new signup for admin purposes. - Allocate 100MB of storage space to the user The File Manager - Allow the user to upload any file type providing they do not go over their space allocation. - Offer multiple file uploads. - After the file has been uploaded, display the URL of where the file is stored, for example [login to view URL] - Allow user to create subdirectories. - Allow user to e-mail others with links to their files. - Allow user to delete any unwanted files. Admin Control. - Allow the administrator to view how many users are current. - Delete and Suspend user accounts. - Increase the amount of space allocated to a user. Hopefully the service will be coded in PHP. I have found almost all of the features listed above in PHP file managers which I have downloaded, but not one that combines all of them.