Introduction to Ajax

In VCL for PHP, Ajax technology is handled in different ways (xajax and qooxdoo RPC), but it's encapsulated enough so you don't have to mess with javascript code. In any case, it's useful to know how it's working behind the scenes, here you can find a nice introduction:

"AJAX (Asynchronous Javascript and XML) is like DHTML in that it is a combination of several existing technologies rather than being a single technology. In this case the technologies involved are Javascript, a server side language to handle the request, and a markup language to return the requested data with."

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