Question on HTML "state" and ability to interact with server

Hello, I've been programming in PHP for about a year, now, experience which has helped me get a job as a programmer at a local company here in town. However, they are a MS .Net shop, and I've had to, needless to say, adapt my experience fairly extensively. Fortunately, I also have some very professional programmers who are keeping me very disciplined in good coding style, and I've had ample opportunity to learn a lot about programming approaches which I am applying to my PHP coding at home. One thing which I'm curious about, and I'm hoping someone here can direct me to some good resources, is .Net's "Code Behind" and "Post Back" behaviors. The net effect (forgive the pun, it was unintentional) is to allow the .aspx page to NOT be stuck in the static state of a typical HTML page. For instance, I am working on a program right now that includes drill-down menus, and the essence of the feature I'm describing is: I am able to NOT load the potential values of the drill-down target until the first drop-down menu has an item selected. At this point, the web server calls a stored procedure with the criterion of the first drop-down menu and the resulting values are returned to build the 2nd drop-down menu. Now all of this is done without the same refresh, and in fact I am told that the page IS NOT being loaded at all, but only the information for that menu. I am assuming this is something only featured in Internet Explorer, but I was wondering if there were something I could look at to do something similar in PHP? The only things I could think of always led me to the same conclusion, the HTML page won't render until all of the code has been run, server side, and any updates of content would result in the entire page, and therefore its state, being re-rendered in the browser. Can someone tell me of some good resources discussing this behavior, and whether it is or might one day be supported by PHP? Back in my HTML-only, pre-PHP days, I made non-Explorer browsers load content dynamically using DHTML by sending the contents of a URL to a layer after I entered text and clicked a button, so hypothetically PHP might fit in that scheme. If anyone can point me in the right direction, I would be greatly appreciative.... _________________________ Vania Smrkovski Internet Design and Programming http://pandorasdream.com/