While discussing this problem, other issues arise, such as: Should the program allow the user to restore this file or retain the existing file? If the file exists, then should I copy the file as a new version? How do I manage files, if the user uploads files of same name and type more than once?

Prerequisites
To understand this article, you should have a fair knowledge of PHP. To run examples given in your machine, you need Apache, PHP, and MySQL installed and configured.

Here's what we want to accomplish:

• When a user uploads a file for the first time, the system should upload the file in the specified folder and insert file details (file name, size, and type) in the database table.
  
  
• When the user uploads a file for the second time (the filename has to be the same), the system will compare the size, date and time of the existing file and of the file being uploaded, and automatically assign a new version for the uploaded file if there is a difference. If there is no difference, then the existing file will be retained and a message will be displayed for the user.
  
  
• A check box allows the user to replace the existing file. Clicking this option will replace the existing file. Note that only the latest version of the file can be replaced in this case, and not an older one.
  
  
• The database will maintain file list and version details. Users should be able to view all the versions of a file and download the required version.
  
  
• While displaying the file list, the program displays all the versions of files under one name. For example, if the file name is xyz.doc and its other versions are xyz_VERSION1.doc, xyz_VERSION2.doc, xyz_VERSION3.doc, and so on, the program will display the filename as xyz.doc for all the versions.
  
  
• The program allows users to delete the file. Clicking on delete will ask for confirmation before proceeding.