Rails-like PHP url router (by: Dan Sosedoff, originally posted at: http://blog.sosedoff.com/2009/09/20/rails-like-php-url-router/ )

classes.php

<?php

define('ROUTER_DEFAULT_CONTROLLER', 'home');
define('ROUTER_DEFAULT_ACTION', 'index');
 
class Router {
	public $request_uri;
	public $routes;
	public $controller, $controller_name;
	public $action, $id;
	public $params;
	public $route_found = false;
 
	public function __construct() {
		$request = $_SERVER['REQUEST_URI'];
		$pos = strpos($request, '?');
		if ($pos) $request = substr($request, 0, $pos);
 
		$this->request_uri = $request;
		$this->routes = array();
	}
 
	public function map($rule, $target=array(), $conditions=array()) {
		$this->routes[$rule] = new Route($rule, $this->request_uri, $target, $conditions);
	}
 
	public function default_routes() {
		$this->map('/:controller');
		$this->map('/:controller/:action');
		$this->map('/:controller/:action/:id');
	}
 
	private function set_route($route) {
		$this->route_found = true;
		$params = $route->params;
		$this->controller = $params['controller']; unset($params['controller']);
		$this->action = $params['action']; unset($params['action']);
		$this->id = $params['id']; 
		$this->params = array_merge($params, $_GET);
 
		if (empty($this->controller)) $this->controller = ROUTER_DEFAULT_CONTROLLER;
		if (empty($this->action)) $this->action = ROUTER_DEFAULT_ACTION;
		if (empty($this->id)) $this->id = null;
 
		$w = explode('_', $this->controller);
		foreach($w as $k => $v) $w[$k] = ucfirst($v);
		$this->controller_name = implode('', $w);
	}
 
	public function execute() {
		foreach($this->routes as $route) {
			if ($route->is_matched) {
				$this->set_route($route);
				break;
			}
		}
	}
}

class Route {
	public $is_matched = false;
	public $params;
	public $url;
	private $conditions;
 
	function __construct($url, $request_uri, $target, $conditions) {
		$this->url = $url;
		$this->params = array();
		$this->conditions = $conditions;
		$p_names = array(); $p_values = array();
 
		preg_match_all('@:([\w]+)@', $url, $p_names, PREG_PATTERN_ORDER);
		$p_names = $p_names[0];
 
		$url_regex = preg_replace_callback('@:[\w]+@', array($this, 'regex_url'), $url);
		$url_regex .= '/?';
 
		if (preg_match('@^' . $url_regex . '$@', $request_uri, $p_values)) {
			array_shift($p_values);
			foreach($p_names as $index => $value) $this->params[substr($value,1)] = urldecode($p_values[$index]);
			foreach($target as $key => $value) $this->params[$key] = $value;
			$this->is_matched = true;
		}
 
		unset($p_names); unset($p_values);
	}
 
	function regex_url($matches) {
		$key = str_replace(':', '', $matches[0]);
		if (array_key_exists($key, $this->conditions)) {
			return '('.$this->conditions[$key].')';
		} 
		else {
			return '([a-zA-Z0-9_\+\-%]+)';
		}
	}
}

usage.php

<?php

require_once 'classes.php';

$r = new Router(); // create router instance 
 
$r->map('/', array('controller' => 'home')); // main page will call controller "Home" with method "index()"
$r->map('/login', array('controller' => 'auth', 'action' => 'login'));
$r->map('/logout', array('controller' => 'auth', 'action' => 'logout'));
$r->map('/signup', array('controller' => 'auth', 'action' => 'signup'));
$r->map('/profile/:action', array('controller' => 'profile')); // will call controller "Profile" with dynamic method ":action()"
$r->map('/users/:id', array('controller' => 'users'), array('id' => '[\d]{1,8}')); // define filters for the url parameters
 
$r->default_routes();
$r->execute();


$router = new Router();
// ... some configs ...
$controller = $router->controller; // will return name as it appears in url, ex: 'user_images'
$controller = $router->controller_name; // will return processed name of controller
// for example, if class name in url is 'user_images', then 'controller_name' var will be UserImages
$router->action;
$router->id; // if parameter :id presents
$router->params; // array(...)
$router->route_matched; // true - if route found, false - if not