Root-based Taxonomy URLs Plugin for WordPress

rootbased-taxonomy-urls.php

<?php
/*
 * Plugin Name: Root-based Taxonomy URLs for WordPress
 * Description: Enables root-based Taxonomy URLs, i.e. Makes /taxonomy/my-taxonomy/ URLs route as /my-taxonomy/
 * Author: Mike Schinkel
 * Author URI: http://about.me/mikeschinkel
 * Plugin URI: https://gist.github.com/1421235
 * Version: 0.1
 * License: GPL 2+
 * Notes: Must use register_root_based_taxonomy_url( $taxonomy[, $priority] ) in an 'init' hook to specify root_based taxonomy.
 */

class Rootbased_Taxonomy_URLs {
  static $root_based_taxonomies = array();

  static function register( $taxonomy, $priority = 10 ) {
    self::$root_based_taxonomies[$taxonomy] = $priority;
  }
  static function on_load() {
    add_filter( 'request', array( __CLASS__, 'request' ) );
    add_filter( 'term_link', array( __CLASS__, 'term_link' ), 10, 3 );
  }
  static function request( $query_vars ) {
    global $wp;
    if ( isset( $query_vars['error'] ) && '404' == $query_vars['error'] ) {
      $taxonomy = self::get_term_taxonomy( $wp->request );
      if ( ! is_null( $taxonomy ) ) {
        $query_vars = array(
          $taxonomy => $wp->request,
          'taxonomy' => $taxonomy,
        );
      }
    } else if ( 1 == count( $query_vars ) ) {
      $taxonomy = self::get_term_taxonomy( reset( $query_vars ) );
      if ( $taxonomy ) {
        wp_safe_redirect( self::term_link( $wp->request, null, $taxonomy ), 301 );
        exit;
      }
    }
    return $query_vars;
  }
  static function term_link( $term_link, $term, $taxonomy ) {
    $taxonomy_object = get_taxonomy( $taxonomy );
    $taxonomy_slug = isset( $taxonomy_object->rewrite['slug'] ) ? $taxonomy_object->rewrite['slug'] : $taxonomy;
    $term_link = preg_replace( "#^(http(s?)://[^/]+/)?{$taxonomy_slug}/#", '$1', $term_link );
    return preg_match( '#^http(s?)://#', $term_link ) ? $term_link : "/{$term_link}";
   }
  static function get_term_taxonomy( $term ) {
    global $wpdb;
    asort( self::$root_based_taxonomies );
    $root_based_taxonomies = array_keys( self::$root_based_taxonomies );
    $where_taxonomies = implode( "','", $root_based_taxonomies );
    $orderby_taxonomies = implode( ',', $root_based_taxonomies );
    $sql =<<<SQL
SELECT
  tt.taxonomy
FROM
  {$wpdb->term_taxonomy} tt
  INNER JOIN {$wpdb->terms} t ON tt.term_id=t.term_id
WHERE 1=1
  AND tt.taxonomy IN ('{$where_taxonomies}')
  AND t.slug = '%s'
ORDER BY
  FIND_IN_SET( tt.taxonomy, '{$orderby_taxonomies}' )
SQL;
    $taxonomy = $wpdb->get_var( $wpdb->prepare( $sql, $term ) );
    return $taxonomy;
  }
}
Rootbased_Taxonomy_URLs::on_load();

function register_root_based_taxonomy_url( $taxonomy, $priority = 10 ) {
  Rootbased_Taxonomy_URLs::register( $taxonomy );
}