Site navigation concept
In the past I have always done my site nav using a switch statement applied to a $_GET['nav'] to determine content to display.
I am about to start a new project and wanted to know what the current preferred method of managing site navigation was.
Using switch is just fine as long as the design of the site is rather simple/basic. If you plan on making it a bit larger with more functionality, your best bet is structuring it with modules. Then, in place of your switch, you'll simply have the main index file which is always ran, and will fetch a variable from your address bar to define location. Doing so will tell your script which module file/folder to include and load the page from.