Kenneth Downs wrote: > We've all seen the amazing results you can get when you start using > Ajax, they all come down to one thing: speed. > > Question is, how is such a speed-up accomplished? The standard answer > is that a complete trip to the server is averted, but this is not true, > in fact a complete cycle does occur: > > 1) Request to server > 2) Possible db access on server > 3) rendering of HTML on server > 4) delivery to browser > 5) re-rendering of portions of screen
The simple answer is that each ajax request is usually much more lightweight than a complete page refresh. You're avoiding the overhead of re-generating all the surrounding content on the server, sending it to the client and rendering it in the browser. As an example, a simple pair of linked select boxes. The category the client selects in the first will change the items available in the second. 1. Traditional Method When changing the first select box, the form is automatically submitted the server, which then renders a complete new page (based on the selected category) and sends it to the client. The client then displays the updated page. 2. Ajax Method When changing the first select box, javascript requests an updated list of items from the server, which generates the list and sends it to the client. Javascript then repopulates the second select box. So we've done less work on the server, transferred less data and saved time on the client, by reloading only a fraction of the data on the page, rather than the whole thing. Dan _______________________________________________ New York PHP Community Talk Mailing List http://lists.nyphp.org/mailman/listinfo/talk NYPHPCon 2006 Presentations Online http://www.nyphpcon.com Show Your Participation in New York PHP http://www.nyphp.org/show_participation.php
