Create a rule for how a URL should be routed including the view name and the $_GET variables to set

router.php

<?php

function getViewPath($routes, $requestUri) {
	// extract the path part of our url (e.g. '/news/3/1')
	// and trim slashes
	$url = trim( parse_url($requestUri, PHP_URL_PATH), '/');
	if ($url == '') {
		return 'views/home.php';
	}
	// get the values sent in the url
	$parts = explode('/', $url);
	// the first part is the view file name
	$viewName = $parts[0];
	$viewPath = "views/$viewName.php";
	// make sure the path does not have a "http://" or ".."
	// so we won't include a remote file or a file in a directory above
	if (
		strpos($viewPath, '://') !== false 
		|| strpos($viewPath, '..') !== false 
		|| !is_file($viewPath)
	) {
		return false;
	}
	// get the route we should use
	$route = $routes[$viewName];
	// ignore the first part, that was our view name
	$varValues = array_slice($parts, 1);
	$varNames = explode('/', $route);
	// go through each var name in the route
	foreach ($varNames as $i => $name) {
		$_GET[$name] = $_REQUEST[$name] = @$varValues[$i];
	}
	return $viewPath;
}

// here define new routes
$routes = array(
	'news' => 'id/page',
	'contact' => 'action/id',
	'blog' => 'year/month/day/post_id/post_name',
	// ...
);

// get the view path. If false, send 404 otherwise include file
$viewFile = getViewPath($routes, $_SERVER['REQUEST_URI']);
if (!$viewFile) {
	header('HTTP/1.0 404 Not Found');
	die;
}
include($viewFile);

Reference: http://forums.devnetwork.net/viewtopic.php?f=1&t=135475&p=676056

The $routes array has keys that represent the view file to use; it has values that represent the names of the variables to save to $_GET and $_REQUEST.

Example usage: getViewPath($routes, '/news/3/1'); returns "views/news.php" and sets $_GET['id'] = "3" and $_GET['page'] = "1".

Also, consider making a converse function that takes a view name and an associative array and returns a url. e.g. url('news', array('id'=>3, 'page'=>1)) would return "/news/3/1". That will reduce chance of error and allow you to change your routing scheme any time.