I use the great CodeIgniter, PHP Framework a lot, Most site’s now days I create use it. One of the many good things is that way it handles pages request’s and PHP $_SERVER['REQUEST_URI'] to find which page we are on.

Here is how it works;

http://www.sheldon.lendrum.co.nz/posts/my-segment/my-page/15/2009/12

Now the way we do things, is break the site up, based on the ‘segments or the URI.
EG:
I am in the ‘posts ( segment 1 )’ part of the site. from ther directs to to the particular post I am on.

Here is some VERY simple javascript to find out any segment I am in.

var currentLocation = window.location.toString();  // find out what page we are on
var hostName = 'http://'+ window.location.hostname; // find our current domain name
var uriString = currentLocation.replace(hostName, '');  // get our segments minus our domain name
var uriSegment = uriString.split('/'); create our segment array

A simple example of usage would be, if you were using a GREAT MOOTOOLS accordion for your navigation, and having one open, based on the address of your page

// set out Accordion toggler elements
var togglers = $$('h3.toggler');

// set out menu var
var showMenu;

// loop our toggler elements, and see if our URI segment matches their name ( in my example. )
togglers.each(function(item, index){
        if(item.get('html').toLowerCase() == uriSegment[1]) showMenu = index;
});

// if our URI segment matched nothing, set a default ( closed in my example )
if(showMenu == undefined) showMenu = -1;

// create our Accordion
new Accordion(togglers , $$('ul.element'), {
        duration: 250,
        display: showMenu,
        initialDisplayFx: false,
        onActive: function(toggler, element) {
                toggler.set('class', 'active');
        },
        onBackground: function(toggler, element) {
              toggler.set('class', '');
        }
});