Core PHP Programming, Third Edition

27.9. URLs Friendly to Search Engines

Search engines such as Google <http://www.google.com/> and All the Web <http://www.alltheweb.com/> attempt to explore the entire Web. They have become an essential resource for Internet users, and anyone who maintains a public site benefits from being listed. Search engines use robots, or spiders, to explore pages in a Web site, and they index PHP scripts the same way they index HTML files. When links appear in a page, they are followed. Consequently, the entire site becomes searchable.

Unfortunately, many robots do not follow links that appear to contain form variables. Links containing question marks may lead a robot into an endless loop, so they are programmed to avoid them. This presents a problem for ...