gistfile1.php

<?php

class Route {

    public $name;
    public $uri_templates = array();
    public $params = array();
    
    public function __construct($name, $uri_templates) {
        $this->name = $name;
        $this->uri_templates = $uri_templates;
    }

    public function match($uri_path_info, $request_params = array()) {
        foreach($this->uri_templates as $uri_template) {
            $regex = $uri_template;
            $regex = preg_replace('/(\{\?[^\/]+\})/', '', $regex);
            $regex = preg_replace('/(\{[^\/]+\})/', '([^/]+)', $regex);
            $regex = str_replace('~', '\~', $regex);
            $match = preg_match('~^'.$regex.'/?$~', $uri_path_info, $vals);
            if($match) {
                // Parse URI Template
                preg_match_all('/\{([^?\}]*)\}/', $uri_template, $keys);
                if(count($keys[1]) && count($vals) > 1){
                    $this->params = array_combine($keys[1], array_slice($vals,1));
                }
                if(count($request_params)) {
                    // Pull query params from URL
                    preg_match('/\{\?([^\}]*)\}/', $uri_template, $valid_keys);
                    if(count($valid_keys)) {
                        $valid_keys = explode(',', $valid_keys[1]);
                        foreach($request_params as $qk => $qv) {
                            if(in_array($qk, $valid_keys)) {
                                $this->params[$qk] = $qv;
                            }
                        }
                    }
                }
                break;
            }
        }
        return $match;
    }
    
    public function getUri($params = null) {
        $params = $params ?: $this->params;
        $url = $this->uri_templates[0];
        $url_params = array();
        if(is_array($params)) {
            foreach($params as $k => $v) {
                $regex = '/(\{'.$k.'\})/';
                if(preg_match($regex, $url)) {
                    $url = preg_replace($regex, $v, $url);
                } else {
                    $url_params[$k] = $v;
                }
            }
        }
        $url = preg_replace('/(\{[^\/]+\})/', '', $url);
        if(count($url_params)) {
            $url .= strpos('?', $url) > 0 ? '' : '?';
            $url .= http_build_query($url_params);
        }
        return $url;
    }

}

# =============================================================================
# USAGE
# =============================================================================

$routes = array(
    'home'            => '/',
    'session-create'  => '/login',
    'session-destroy' => '/logout',
    'users'           => '/users',
    'user'            => '/user/{id}',
    'messages'        => '/messages',
    'messages-new'    => '/messages/new',
    'message'         => '/message/{id}',
    'message-remove'  => '/message/{id}/remove',
    'search'          => '/search{?q}'
);

$uri_parts = explode('?', $_SERVER['REQUEST_URI']);
$path   = $uri_parts[0];
$params = $_GET;

$matched_route = null;
foreach($routes as $name => $uri_template) {
    $route = new Route($name, array($uri_template));
    if($route->match($path, $params)) {
        $matched_route = $route;
        break;
    }
}

if($matched_route) {
    echo "Matched route: " . $matched_route->name . "<br/>";
    echo "URL: "           . $matched_route->getUri() . "<br/><br/>";
    
    $msg_route  = new Route('message', array($routes['message']));
    echo "Message URL: " . $msg_route->getUri(array('id' => '123')) . "<br/><br/>";
    
    $user_route = new Route('user', array($routes['user']));
    echo "User URL: " . $user_route->getUri(array('id'  => '456')) . "<br/>";
} else {
    throw new Exception('404');
}

In real life you'd probably have a router that manages these routes but you get the gist.

Oh and here's a running demo of this script
http://gist.hackyhack.net/
http://gist.hackyhack.net/search?q=bananas
http://gist.hackyhack.net/users
http://gist.hackyhack.net/logout

This is exactly what I was looking for. I used url generation and matching from Symfony, but it doesn't have the detail that your solution has. I'm going to merge this code into ScaleUp ( WordPress-ish framework for building web apps ) when I work on routes again.

This is awesome, unfortunately it doesn't match all RFC 6570 templates (e.g. {+path}/here should match against /foo/bar/here and {/var:1,var} should match against /f/bar). Am I wrong?

@heruan - You are correct. This is a partial implementation.