One of the things that all programmers love is to write a program which writes another program. On the web we have two different programming environments: the client (browser) and the server. Due to the HTTP protocol definition we can write a program on the server which writes another program to be executed on the client. Let's pick PHP (of course) for the server and JavaScript for the client. We'll show you in this article how you can use this scheme to store data in the client and then minimize the data transfered between the server and the browser for interactive applications like a chat room, a news system or whatever you want.