CakePHP routing based on slug

routes.php

<?php
App::import('Lib', 'routes/SluggableRoute');

Router::connect(
	'/path-alias/:slug/*',
	array(
		'controller' => 'controller_name',
		'action' => 'action_name',
		'model' => 'ModelName',
	),
	array(
		'slug' => '[\w-]+',
		'routeClass' => 'SluggableRoute',
	)
);

sluggable_route.php

<?php

/**
 * Handle routes with a slug component from a model attribute.
 *
 * @see https://gist.github.com/4069038
 */
class SluggableRoute extends CakeRoute {

	protected $cache_items = null;

	function match($url) {
		// CakeRoute::match() expects model to be provided in $url to determine
		// the correct route, but controller & action are enough if multiple
		// models don't use the same route.
		$url['model'] = $this->defaults['model'];

		if ($url['action'] != $this->defaults['action'] || $url['controller'] != $this->defaults['controller']) {
			return false;
		}

		// if an item's id was passed in instead of it's slug, translate it.
		if (!isset($url['slug']) && isset($url[0])) {

			$model = $url['model'];
			$id = $url[0];


			if (is_null($this->cache_items)) {
				$this->cache_items = Cache::read('SluggableRoute.' . $model);
			}
			if (!empty($this->cache_items) && false !== ($slug = array_search($id, $this->cache_items))) {
				// $slug already set in conditional
			}
			else {
				App::import('Model', $model);
				list($plugin, $model) = pluginSplit($model);
				$Model = new $model;

				$item = $Model->find('first', array(
					'fields' => array('slug'),
					'conditions' => array(
						$Model->alias . '.id' => $id,
					),
					'contain' => array(),
					'recursive' => -1,
				));

				if (empty($item)) {
					return false;
				}

				$slug = $item[$Model->alias]['slug'];

				if (empty($this->cache_items)) {
					$this->cache_items = array();
				}
				$this->cache_items[$slug] = $id;

				Cache::write('SluggableRoute.' . $model, $this->cache_items);
			}

			$url['slug'] = $slug;
			unset($url[0]);
		}

		return parent::match($url);
	}

	function parse($url) {
		$params = parent::parse($url);

		if (empty($params) || empty($params['model']) || empty($params['slug'])) {
			return false;
		}

		$model = $params['model'];
		$slug = $params['slug'];

		if (is_null($this->cache_items)) {
			$this->cache_items = Cache::read('SluggableRoute.' . $model);
		}
		if (!empty($this->cache_items) && array_key_exists($slug, $this->cache_items)) {
			$id = $this->cache_items[$slug];
		}
		else {

			App::import('Model', $model);
			list($plugin, $model) = pluginSplit($model);
			$Model = new $model();

			$item = $Model->find('first', array(
				'fields' => array('id', 'slug'),
				'conditions' => array(
					$Model->alias . '.slug' => $slug,
				),
				'contain' => array(),
				'recursive' => -1,
			));

			$id = ($item) ? $item[$Model->alias]['id'] : false;

			if (empty($this->cache_items)) {
				$this->cache_items = array();
			}
			$this->cache_items[$slug] = $id;

			Cache::write('SluggableRoute.' . $model, $this->cache_items);
		}

		if (!$id) {
			return false;
		}

		$params['pass'] = array(
			$id,
		);
		return $params;
	}
}