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Reverse Routing (based on DrF Reverse Routing)

I have developed a new reverse routing extension based on the awesome DrF Reverse Routing (forum post, wiki page). If you have doubts about what reverse routing is, check out the forum post.


- Cached route data: The routing configuration is grabbed and parsed once per request, not every time site_url() is called
- Extension of CI_Config instead of url_helper (url_helper was just calling CI_Config anyway)
- Code refactoring: Removed unused variables, reduced lines of code a bit

Tested on

PHP 5.2 (written with PHP 4 in mind)
Codeigniter 1.7.2

The Code (extension of CI_Config)

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');
* Reverse routing
* Based on DrF Reverse Routing (http://drfloob.com/)

* @author  Matt Alexander
* @link    http://mattalexander.me

// ------------------------------------------------------------------------

* App Config Class
class MY_Config extends CI_Config {

     * Site URL
     * @access    public
     * @param    string or array    the URI
     * @return    string
    function site_url($uri = '')
        // Clean up $uri
        if (is_array($uri)) {
            $uri = implode('/', $uri);
        $uri = trim($uri, '/');

        // Loop through routes to check for back-references
        $routes = $this->reverse_routes();
        foreach ($routes as $route) {
            if (preg_match($route['uri_pattern'], $uri)) {
                $rewritten_uri = preg_replace($route['uri_pattern'], $route['rewritten'], $uri);
                return parent::site_url($rewritten_uri);
        // Nothing found
        return parent::site_url($uri);
     * Retrieve reverse routes
     * @access    public
     * @return    array
    function reverse_routes()
        // Cache routes
        static $routes;
        if (!is_null($routes)) {
            return $routes;

        // Get config routes
        $config_routes =& load_class('Router')->routes;
        unset($config_routes['default_controller'], $config_routes['scaffolding_trigger']);

        // Loop through routes to check for back-references
        $routes = array();
        foreach ($config_routes as $route_pattern => $route_destination) {

            // Every non-literal piece of regex needs to be within a backreference because the
            // parentheses themselves are used to find the regex parts.
            // So just add it straight to the array for literal matching.
            if (preg_match('/[^\(][.+?{\:]/', $route_pattern)
                || strpos($route_pattern, '(') === FALSE
                || strpos($route_destination, '$') === FALSE
                ) {
                $routes[] = array(
                    'uri_pattern' => '#^'.$route_destination.'$#',
                    'rewritten' => $route_pattern,
            $route_pattern = str_replace(array(':any', ':num'), array('.+?', '[0-9]+'), $route_pattern);
            // Find all back-references in route pattern
            preg_match_all('/(\(.+?\))/', $route_pattern, $matches);
            $route_pattern_backreferences = array();
            foreach ($matches[1] as $i => $match) {
                $n = $i + 1;
                $route_pattern_backreferences[$n] = $match;

            // Find all references in route destination
            // Also, create an array that keeps the order of references
            preg_match_all('/\$(\d+?)/', $route_destination, $matches);
            $route_destination_references = array();
            $reference_order = array();
            foreach ($matches[1] as $n) {
                $route_destination_references[$n] = '$'.$n;
                $reference_order[] = $n;
            // Create a rewritten URL for use as the second paramater of preg_replace
            $rewritten = $route_pattern;
            foreach ($reference_order as $n) {
                $rewritten = preg_replace('/(\(.+?\))/', '\\'.$route_destination_references[$n], $rewritten, 1);
            $uri_pattern = $route_destination;
            foreach ($route_destination_references as $n => $reference) {
                if (isset($route_pattern_backreferences[$n])) {
                    $uri_pattern = str_replace($reference, $route_pattern_backreferences[$n], $uri_pattern);
            $uri_pattern = '#^'.$uri_pattern.'$#';
            $routes[] = array(
                'uri_pattern' => $uri_pattern,
                'rewritten' => $rewritten,
        return $routes;

Constructive criticism? Bug report?

My question might be trivial but I have been doing CI just for couple days now.
I am having difficulties to initiate MY_Config at all.

I do understand that to make it happen automatically I have to have:

$config['subclass_prefix'] = 'MY_';

Is there anything I am missing?

Make sure you're putting it in the right place:
/Application/Core ... ran into a similar problem the other day because I was trying to stuff it into /System/Core....


Thanks a lot for a tip. Problem has been sorted. Not sure what caused the issue. Haven't tested routing yet as I am busy with other things at the moment but all ready and loaded. I added test_me() method inside MY_Controller that returns string to make sure all is good as without routing couldn't test. I will be testing this module next week probably along with my multimodule url so will try to place a little comment.

Doesn't work for me, unfortunately. Mattalexx, could you be so kind and zip your solution, or at least provide step-by-step guide for CodeIgniter2?

[quote author="Alexander84" date="1299898489"]Doesn't work for me, unfortunately. Mattalexx, could you be so kind and zip your solution, or at least provide step-by-step guide for CodeIgniter2?[/quote]

I have a project coming up that calls for CI. I'll get it working in CI 2 and post here, so make sure you're subscribed to the thread.

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