This snippet extracts the keywords or search phrases from a Google referral. It also sets variables for the search engine, date and web page which received the referral if you want to log the data to a file or database. The variables are $engine, $finalphrase (keyword phrase), $page(referred web page), and $date.

If a visitor comes to your site from a search engine such as Google or Yahoo, this function will highlight the keywords in a given text the user used for his search.