Is it possible using php ?

A server and client are connected using a 35kbps PPP link. A user on the client side types the URL of a mpeg file on the location bar. The same file is also existing in $DIR of the client (windows) system. Now, since the file is already there on the local hard disk of the client, the file need not be downloaded through the PPP link, instead be played from the local disk - which makes faster access ! It is something like this: if file available locally, then use that file else send the file present in the location as given by the URL Is there a way to do this from the server side using php. Or using any other tool, can we do it on the client side - that is, say, some program always runs in the background and whenever a URL is entered, the $DIR is checked to see if the file is present else it is retrieved from the location. All this should be transparent to the user. Can anyone help me please ? Regards, Uma