The NETTUTS.com site has a new tutorial posted today showing how to combine jQuery and PHP to add auto complete functionality to a simple search engine.

This tutorial will show you how to use the "Popular Queries" feed from your Google Custom Search Engine (CSE) as a data source for a jQuery autocomplete.

They walk through the creation of the search page and provide the code for the jQuery half that calls the autocomplete() method on the search field. The PHP script that's called loads the XML file from Google's server with the latest from the "Popular Queries" page. This is then parsed and sent back out as Javascript back to the waiting jQuery. They also include a brief look at caching the results by writing them out to a file that's checked and updated based on the results of a filectime() call.