NOt possible at all, or not sensibly anyway.
PHP is a server-side scripting language and only executes on the server. You cannot sedn php code to the client and have it execute there.
Yes you can upload and download files through http post, or FTP, or the like, and move them around the client machine that way. Sound silly? IT should do.
To do it with a client-side scripting language you really are going to need VBScript/ASP/C#/.NET/Java/ActiveX or the like.