a program that performs automated backups of an end-user's hard disk, and allows them to retrieve backups of same from a web-server?

edit: even if PHP isn't the most optimal language to use for this project, is it still possible? and, without getting the thread too side-tracked, i'm open to hearing suggestions for languages that'd be more suitable for the task.

It would require some type of desktop application - .NET, Java, C++, maybe even Adobe AIR

PHP could process the data, but you would need a desktop application to actually retrieve and submit the data to the server. Server side code only interacts with data sent from the user, usually from the browser. It cannot interact directly with a user's machine.

While it is technically possible with PHP it'd be a huge PITA and slow.

A quck and dirty way to do it would be to use a SCM (version control) like Git or Mercurial. This would be really easy and you could restore things to a given point in time.

Another popular option is rsync

Veritas backup Exec and deploy the remote agents to the desktop machines that require backing up.

I suppose it COULD technically be done in only PHP, but like the above posters said, it would not be the most optimal way to do it. Java would be great for this kind of thing; it's simple to use, and pretty fast.

The way I would assume to do it is this:
-Establish a connection to the end-user's computer via FTP
-FTP the files over from your server to their computer
-Run a script (somehow) to move those files where you want them

But the average user won't know what an 'FTP' and definitely won't know how to set one up.

-FTP the files over from your server to their computer

Actually what the OP wants to is the other way around so it copies files FROM the client workstation TO the server.

Originally Posted by chrishirst

Actually what the OP wants to is the other way around so it copies files FROM the client workstation TO the server.

Oh, so I see! Sorry about that

In that case, I'd have no idea on how to do that with just PHP. You'd have to keep a constant connection to the client's computer via something, and check every-so-often if the file has changed.

check every-so-often if the file has changed.

Which can't be done with PHP. You would need a client application running on the remote machine to pass the files to the server.

Originally Posted by chrishirst

Which can't be done with PHP. You would need a client application running on the remote machine to pass the files to the server.

I suppose you could have a package with PHP inside it that would run scripts in CLI mode. But you still would need an entity that would invoke it from a bat file or something.