wp-includes/canonical.php

   1 <?php
   2 /**
   3  * Canonical API to handle WordPress Redirecting
   4  *
   5  * Based on "Permalink Redirect" from Scott Yang and "Enforce www. Preference"
   6  * by Mark Jaquith
   7  *
   8  * @package WordPress
   9  * @since 2.3.0
  10  */
  11
  12 /**
  13  * Redirects incoming links to the proper URL based on the site url.
  14  *
  15  * Search engines consider www.somedomain.com and somedomain.com to be two
  16  * different URLs when they both go to the same location. This SEO enhancement
  17  * prevents penalty for duplicate content by redirecting all incoming links to
  18  * one or the other.
  19  *
  20  * Prevents redirection for feeds, trackbacks, searches, comment popup, and
  21  * admin URLs. Does not redirect on IIS, page/post previews, and on form data.
  22  *
  23  * Will also attempt to find the correct link when a user enters a URL that does
  24  * not exist based on exact WordPress query. Will instead try to parse the URL
  25  * or query in an attempt to figure the correct page to go to.
  26  *
  27  * @since 2.3.0
  28  * @uses $wp_rewrite
  29  * @uses $is_IIS
  30  *
  31  * @param string $requested_url Optional. The URL that was requested, used to
  32  *              figure if redirect is needed.
  33  * @param bool $do_redirect Optional. Redirect to the new URL.
  34  * @return null|false|string Null, if redirect not needed. False, if redirect
  35  *              not needed or the string of the URL
  36  */
  37 function redirect_canonical( $requested_url = null, $do_redirect = true ) {
  38         global $wp_rewrite, $is_IIS, $wp_query, $wpdb;
  39
  40         if ( is_trackback() || is_search() || is_comments_popup() || is_admin() || !empty($_POST) || is_preview() || is_robots() || $is_IIS )
  41                 return;
  42
  43         if ( !$requested_url ) {
  44                 // build the URL in the address bar
  45                 $requested_url  = is_ssl() ? 'https://' : 'http://';
  46                 $requested_url .= $_SERVER['HTTP_HOST'];
  47                 $requested_url .= $_SERVER['REQUEST_URI'];
  48         }
  49
  50         $original = @parse_url($requested_url);
  51         if ( false === $original )
  52                 return;
  53
  54         // Some PHP setups turn requests for / into /index.php in REQUEST_URI
  55         // See: http://trac.wordpress.org/ticket/5017
  56         // See: http://trac.wordpress.org/ticket/7173
  57         // Disabled, for now:
  58         // $original['path'] = preg_replace('|/index\.php$|', '/', $original['path']);
  59
  60         $redirect = $original;
  61         $redirect_url = false;
  62
  63         // Notice fixing
  64         if ( !isset($redirect['path']) )
  65                 $redirect['path'] = '';
  66         if ( !isset($redirect['query']) )
  67                 $redirect['query'] = '';
  68
  69         if ( is_feed() && ( $id = get_query_var( 'p' ) ) ) {
  70                 if ( $redirect_url = get_post_comments_feed_link( $id, get_query_var( 'feed' ) ) ) {
  71                         $redirect['query'] = _remove_qs_args_if_not_in_url( $redirect['query'], array( 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type', 'feed'), $redirect_url );
  72                         $redirect['path'] = parse_url( $redirect_url, PHP_URL_PATH );
  73                 }
  74         }
  75
  76         if ( is_singular() && 1 > $wp_query->post_count && ($id = get_query_var('p')) ) {
  77
  78                 $vars = $wpdb->get_results( $wpdb->prepare("SELECT post_type, post_parent FROM $wpdb->posts WHERE ID = %d", $id) );
  79
  80                 if ( isset($vars[0]) && $vars = $vars[0] ) {
  81                         if ( 'revision' == $vars->post_type && $vars->post_parent > 0 )
  82                                 $id = $vars->post_parent;
  83
  84                         if ( $redirect_url = get_permalink($id) )
  85                                 $redirect['query'] = _remove_qs_args_if_not_in_url( $redirect['query'], array( 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type' ), $redirect_url );
  86                 }
  87         }
  88
  89         // These tests give us a WP-generated permalink
  90         if ( is_404() ) {
  91
  92                 // Redirect ?page_id, ?p=, ?attachment_id= to their respective url's
  93                 $id = max( get_query_var('p'), get_query_var('page_id'), get_query_var('attachment_id') );
  94                 if ( $id && $redirect_post = get_post($id) ) {
  95                         $post_type_obj = get_post_type_object($redirect_post->post_type);
  96                         if ( $post_type_obj->public ) {
  97                                 $redirect_url = get_permalink($redirect_post);
  98                                 $redirect['query'] = _remove_qs_args_if_not_in_url( $redirect['query'], array( 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type' ), $redirect_url );
  99                         }
 100                 }
 101
 102                 if ( ! $redirect_url ) {
 103                         if ( $redirect_url = redirect_guess_404_permalink() ) {
 104                                 $redirect['query'] = _remove_qs_args_if_not_in_url( $redirect['query'], array( 'page', 'feed', 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type' ), $redirect_url );
 105                         }
 106                 }
 107
 108         } elseif ( is_object($wp_rewrite) && $wp_rewrite->using_permalinks() ) {
 109                 // rewriting of old ?p=X, ?m=2004, ?m=200401, ?m=20040101
 110                 if ( is_attachment() && !empty($_GET['attachment_id']) && ! $redirect_url ) {
 111                         if ( $redirect_url = get_attachment_link(get_query_var('attachment_id')) )
 112                                 $redirect['query'] = remove_query_arg('attachment_id', $redirect['query']);
 113                 } elseif ( is_single() && !empty($_GET['p']) && ! $redirect_url ) {
 114                         if ( $redirect_url = get_permalink(get_query_var('p')) )
 115                                 $redirect['query'] = remove_query_arg(array('p', 'post_type'), $redirect['query']);
 116                 } elseif ( is_single() && !empty($_GET['name'])  && ! $redirect_url ) {
 117                         if ( $redirect_url = get_permalink( $wp_query->get_queried_object_id() ) )
 118                                 $redirect['query'] = remove_query_arg('name', $redirect['query']);
 119                 } elseif ( is_page() && !empty($_GET['page_id']) && ! $redirect_url ) {
 120                         if ( $redirect_url = get_permalink(get_query_var('page_id')) )
 121                                 $redirect['query'] = remove_query_arg('page_id', $redirect['query']);
 122                 } elseif ( is_page() && !is_feed() && isset($wp_query->queried_object) && 'page' == get_option('show_on_front') && $wp_query->queried_object->ID == get_option('page_on_front')  && ! $redirect_url ) {
 123                         $redirect_url = home_url('/');
 124                 } elseif ( is_home() && !empty($_GET['page_id']) && 'page' == get_option('show_on_front') && get_query_var('page_id') == get_option('page_for_posts')  && ! $redirect_url ) {
 125                         if ( $redirect_url = get_permalink(get_option('page_for_posts')) )
 126                                 $redirect['query'] = remove_query_arg('page_id', $redirect['query']);
 127                 } elseif ( !empty($_GET['m']) && ( is_year() || is_month() || is_day() ) ) {
 128                         $m = get_query_var('m');
 129                         switch ( strlen($m) ) {
 130                                 case 4: // Yearly
 131                                         $redirect_url = get_year_link($m);
 132                                         break;
 133                                 case 6: // Monthly
 134                                         $redirect_url = get_month_link( substr($m, 0, 4), substr($m, 4, 2) );
 135                                         break;
 136                                 case 8: // Daily
 137                                         $redirect_url = get_day_link(substr($m, 0, 4), substr($m, 4, 2), substr($m, 6, 2));
 138                                         break;
 139                         }
 140                         if ( $redirect_url )
 141                                 $redirect['query'] = remove_query_arg('m', $redirect['query']);
 142                 // now moving on to non ?m=X year/month/day links
 143                 } elseif ( is_day() && get_query_var('year') && get_query_var('monthnum') && !empty($_GET['day']) ) {
 144                         if ( $redirect_url = get_day_link(get_query_var('year'), get_query_var('monthnum'), get_query_var('day')) )
 145                                 $redirect['query'] = remove_query_arg(array('year', 'monthnum', 'day'), $redirect['query']);
 146                 } elseif ( is_month() && get_query_var('year') && !empty($_GET['monthnum']) ) {
 147                         if ( $redirect_url = get_month_link(get_query_var('year'), get_query_var('monthnum')) )
 148                                 $redirect['query'] = remove_query_arg(array('year', 'monthnum'), $redirect['query']);
 149                 } elseif ( is_year() && !empty($_GET['year']) ) {
 150                         if ( $redirect_url = get_year_link(get_query_var('year')) )
 151                                 $redirect['query'] = remove_query_arg('year', $redirect['query']);
 152                 } elseif ( is_author() && !empty($_GET['author']) && preg_match( '|^[0-9]+$|', $_GET['author'] ) ) {
 153                         $author = get_userdata(get_query_var('author'));
 154                         if ( ( false !== $author ) && $wpdb->get_var( $wpdb->prepare( "SELECT ID FROM $wpdb->posts WHERE $wpdb->posts.post_author = %d AND $wpdb->posts.post_status = 'publish' LIMIT 1", $author->ID ) ) ) {
 155                                 if ( $redirect_url = get_author_posts_url($author->ID, $author->user_nicename) )
 156                                         $redirect['query'] = remove_query_arg('author', $redirect['query']);
 157                         }
 158                 } elseif ( is_category() || is_tag() || is_tax() ) { // Terms (Tags/categories)
 159
 160                         $term_count = 0;
 161                         foreach ( $wp_query->tax_query->queries as $tax_query )
 162                                 $term_count += count( $tax_query['terms'] );
 163
 164                         $obj = $wp_query->get_queried_object();
 165                         if ( $term_count <= 1 && !empty($obj->term_id) && ( $tax_url = get_term_link((int)$obj->term_id, $obj->taxonomy) ) && !is_wp_error($tax_url) ) {
 166                                 if ( !empty($redirect['query']) ) {
 167                                         // Strip taxonomy query vars off the url.
 168                                         $qv_remove = array( 'term', 'taxonomy');
 169                                         if ( is_category() ) {
 170                                                 $qv_remove[] = 'category_name';
 171                                                 $qv_remove[] = 'cat';
 172                                         } elseif ( is_tag() ) {
 173                                                 $qv_remove[] = 'tag';
 174                                                 $qv_remove[] = 'tag_id';
 175                                         } else { // Custom taxonomies will have a custom query var, remove those too:
 176                                                 $tax_obj = get_taxonomy( $obj->taxonomy );
 177                                                 if ( false !== $tax_obj->query_var )
 178                                                         $qv_remove[] = $tax_obj->query_var;
 179                                         }
 180
 181                                         $rewrite_vars = array_diff( array_keys($wp_query->query), array_keys($_GET) );
 182
 183                                         if ( !array_diff($rewrite_vars, array_keys($_GET))  ) { // Check to see if all the Query vars are coming from the rewrite, none are set via $_GET
 184                                                 $redirect['query'] = remove_query_arg($qv_remove, $redirect['query']); //Remove all of the per-tax qv's
 185
 186                                                 // Create the destination url for this taxonomy
 187                                                 $tax_url = parse_url($tax_url);
 188                                                 if ( ! empty($tax_url['query']) ) { // Taxonomy accessible via ?taxonomy=..&term=.. or any custom qv..
 189                                                         parse_str($tax_url['query'], $query_vars);
 190                                                         $redirect['query'] = add_query_arg($query_vars, $redirect['query']);
 191                                                 } else { // Taxonomy is accessible via a "pretty-URL"
 192                                                         $redirect['path'] = $tax_url['path'];
 193                                                 }
 194
 195                                         } else { // Some query vars are set via $_GET. Unset those from $_GET that exist via the rewrite
 196                                                 foreach ( $qv_remove as $_qv ) {
 197                                                         if ( isset($rewrite_vars[$_qv]) )
 198                                                                 $redirect['query'] = remove_query_arg($_qv, $redirect['query']);
 199                                                 }
 200                                         }
 201                                 }
 202
 203                         }
 204                 } elseif ( is_single() && strpos($wp_rewrite->permalink_structure, '%category%') !== false && $cat = get_query_var( 'category_name' ) ) {
 205                         $category = get_category_by_path( $cat );
 206                         $post_terms = wp_get_object_terms($wp_query->get_queried_object_id(), 'category', array('fields' => 'tt_ids'));
 207                         if ( (!$category || is_wp_error($category)) || ( !is_wp_error($post_terms) && !empty($post_terms) && !in_array($category->term_taxonomy_id, $post_terms) ) )
 208                                 $redirect_url = get_permalink($wp_query->get_queried_object_id());
 209                 }
 210
 211                 // Post Paging
 212                 if ( is_singular() && ! is_front_page() && get_query_var('page') ) {
 213                         if ( !$redirect_url )
 214                                 $redirect_url = get_permalink( get_queried_object_id() );
 215                         $redirect_url = trailingslashit( $redirect_url ) . user_trailingslashit( get_query_var( 'page' ), 'single_paged' );
 216                         $redirect['query'] = remove_query_arg( 'page', $redirect['query'] );
 217                 }
 218
 219                 // paging and feeds
 220                 if ( get_query_var('paged') || is_feed() || get_query_var('cpage') ) {
 221                         while ( preg_match( "#/$wp_rewrite->pagination_base/?[0-9]+?(/+)?$#", $redirect['path'] ) || preg_match( '#/(comments/?)?(feed|rss|rdf|atom|rss2)(/+)?$#', $redirect['path'] ) || preg_match( '#/comment-page-[0-9]+(/+)?$#', $redirect['path'] ) ) {
 222                                 // Strip off paging and feed
 223                                 $redirect['path'] = preg_replace("#/$wp_rewrite->pagination_base/?[0-9]+?(/+)?$#", '/', $redirect['path']); // strip off any existing paging
 224                                 $redirect['path'] = preg_replace('#/(comments/?)?(feed|rss2?|rdf|atom)(/+|$)#', '/', $redirect['path']); // strip off feed endings
 225                                 $redirect['path'] = preg_replace('#/comment-page-[0-9]+?(/+)?$#', '/', $redirect['path']); // strip off any existing comment paging
 226                         }
 227
 228                         $addl_path = '';
 229                         if ( is_feed() && in_array( get_query_var('feed'), $wp_rewrite->feeds ) ) {
 230                                 $addl_path = !empty( $addl_path ) ? trailingslashit($addl_path) : '';
 231                                 if ( !is_singular() && get_query_var( 'withcomments' ) )
 232                                         $addl_path .= 'comments/';
 233                                 if ( ( 'rss' == get_default_feed() && 'feed' == get_query_var('feed') ) || 'rss' == get_query_var('feed') )
 234                                         $addl_path .= user_trailingslashit( 'feed/' . ( ( get_default_feed() == 'rss2' ) ? '' : 'rss2' ), 'feed' );
 235                                 else
 236                                         $addl_path .= user_trailingslashit( 'feed/' . ( ( get_default_feed() ==  get_query_var('feed') || 'feed' == get_query_var('feed') ) ? '' : get_query_var('feed') ), 'feed' );
 237                                 $redirect['query'] = remove_query_arg( 'feed', $redirect['query'] );
 238                         } elseif ( is_feed() && 'old' == get_query_var('feed') ) {
 239                                 $old_feed_files = array(
 240                                         'wp-atom.php'         => 'atom',
 241                                         'wp-commentsrss2.php' => 'comments_rss2',
 242                                         'wp-feed.php'         => get_default_feed(),
 243                                         'wp-rdf.php'          => 'rdf',
 244                                         'wp-rss.php'          => 'rss2',
 245                                         'wp-rss2.php'         => 'rss2',
 246                                 );
 247                                 if ( isset( $old_feed_files[ basename( $redirect['path'] ) ] ) ) {
 248                                         $redirect_url = get_feed_link( $old_feed_files[ basename( $redirect['path'] ) ] );
 249                                         wp_redirect( $redirect_url, 301 );
 250                                         die();
 251                                 }
 252                         }
 253
 254                         if ( get_query_var('paged') > 0 ) {
 255                                 $paged = get_query_var('paged');
 256                                 $redirect['query'] = remove_query_arg( 'paged', $redirect['query'] );
 257                                 if ( !is_feed() ) {
 258                                         if ( $paged > 1 && !is_single() ) {
 259                                                 $addl_path = ( !empty( $addl_path ) ? trailingslashit($addl_path) : '' ) . user_trailingslashit("$wp_rewrite->pagination_base/$paged", 'paged');
 260                                         } elseif ( !is_single() ) {
 261                                                 $addl_path = !empty( $addl_path ) ? trailingslashit($addl_path) : '';
 262                                         }
 263                                 } elseif ( $paged > 1 ) {
 264                                         $redirect['query'] = add_query_arg( 'paged', $paged, $redirect['query'] );
 265                                 }
 266                         }
 267
 268                         if ( get_option('page_comments') && ( ( 'newest' == get_option('default_comments_page') && get_query_var('cpage') > 0 ) || ( 'newest' != get_option('default_comments_page') && get_query_var('cpage') > 1 ) ) ) {
 269                                 $addl_path = ( !empty( $addl_path ) ? trailingslashit($addl_path) : '' ) . user_trailingslashit( 'comment-page-' . get_query_var('cpage'), 'commentpaged' );
 270                                 $redirect['query'] = remove_query_arg( 'cpage', $redirect['query'] );
 271                         }
 272
 273                         $redirect['path'] = user_trailingslashit( preg_replace('|/index.php/?$|', '/', $redirect['path']) ); // strip off trailing /index.php/
 274                         if ( !empty( $addl_path ) && $wp_rewrite->using_index_permalinks() && strpos($redirect['path'], '/index.php/') === false )
 275                                 $redirect['path'] = trailingslashit($redirect['path']) . 'index.php/';
 276                         if ( !empty( $addl_path ) )
 277                                 $redirect['path'] = trailingslashit($redirect['path']) . $addl_path;
 278                         $redirect_url = $redirect['scheme'] . '://' . $redirect['host'] . $redirect['path'];
 279                 }
 280
 281                 if ( 'wp-register.php' == basename( $redirect['path'] ) ) {
 282                         if ( is_multisite() )
 283                                 $redirect_url = apply_filters( 'wp_signup_location', site_url( 'wp-signup.php' ) );
 284                         else
 285                                 $redirect_url = site_url( 'wp-login.php?action=register' );
 286                         wp_redirect( $redirect_url, 301 );
 287                         die();
 288                 }
 289         }
 290
 291         // tack on any additional query vars
 292         $redirect['query'] = preg_replace( '#^\??&*?#', '', $redirect['query'] );
 293         if ( $redirect_url && !empty($redirect['query']) ) {
 294                 parse_str( $redirect['query'], $_parsed_query );
 295                 $redirect = @parse_url($redirect_url);
 296
 297                 if ( ! empty( $_parsed_query['name'] ) && ! empty( $redirect['query'] ) ) {
 298                         parse_str( $redirect['query'], $_parsed_redirect_query );
 299
 300                         if ( empty( $_parsed_redirect_query['name'] ) )
 301                                 unset( $_parsed_query['name'] );
 302                 }
 303
 304                 $_parsed_query = rawurlencode_deep( $_parsed_query );
 305                 $redirect_url = add_query_arg( $_parsed_query, $redirect_url );
 306         }
 307
 308         if ( $redirect_url )
 309                 $redirect = @parse_url($redirect_url);
 310
 311         // www.example.com vs example.com
 312         $user_home = @parse_url(home_url());
 313         if ( !empty($user_home['host']) )
 314                 $redirect['host'] = $user_home['host'];
 315         if ( empty($user_home['path']) )
 316                 $user_home['path'] = '/';
 317
 318         // Handle ports
 319         if ( !empty($user_home['port']) )
 320                 $redirect['port'] = $user_home['port'];
 321         else
 322                 unset($redirect['port']);
 323
 324         // trailing /index.php
 325         $redirect['path'] = preg_replace('|/index.php/*?$|', '/', $redirect['path']);
 326
 327         // Remove trailing spaces from the path
 328         $redirect['path'] = preg_replace( '#(%20| )+$#', '', $redirect['path'] );
 329
 330         if ( !empty( $redirect['query'] ) ) {
 331                 // Remove trailing spaces from certain terminating query string args
 332                 $redirect['query'] = preg_replace( '#((p|page_id|cat|tag)=[^&]*?)(%20| )+$#', '$1', $redirect['query'] );
 333
 334                 // Clean up empty query strings
 335                 $redirect['query'] = trim(preg_replace( '#(^|&)(p|page_id|cat|tag)=?(&|$)#', '&', $redirect['query']), '&');
 336
 337                 // Redirect obsolete feeds
 338                 $redirect['query'] = preg_replace( '#(^|&)feed=rss(&|$)#', '$1feed=rss2$3', $redirect['query'] );
 339
 340                 // Remove redundant leading ampersands
 341                 $redirect['query'] = preg_replace( '#^\??&*?#', '', $redirect['query'] );
 342         }
 343
 344         // strip /index.php/ when we're not using PATHINFO permalinks
 345         if ( !$wp_rewrite->using_index_permalinks() )
 346                 $redirect['path'] = str_replace('/index.php/', '/', $redirect['path']);
 347
 348         // trailing slashes
 349         if ( is_object($wp_rewrite) && $wp_rewrite->using_permalinks() && !is_404() && (!is_front_page() || ( is_front_page() && (get_query_var('paged') > 1) ) ) ) {
 350                 $user_ts_type = '';
 351                 if ( get_query_var('paged') > 0 ) {
 352                         $user_ts_type = 'paged';
 353                 } else {
 354                         foreach ( array('single', 'category', 'page', 'day', 'month', 'year', 'home') as $type ) {
 355                                 $func = 'is_' . $type;
 356                                 if ( call_user_func($func) ) {
 357                                         $user_ts_type = $type;
 358                                         break;
 359                                 }
 360                         }
 361                 }
 362                 $redirect['path'] = user_trailingslashit($redirect['path'], $user_ts_type);
 363         } elseif ( is_front_page() ) {
 364                 $redirect['path'] = trailingslashit($redirect['path']);
 365         }
 366
 367         // Strip multiple slashes out of the URL
 368         if ( strpos($redirect['path'], '//') > -1 )
 369                 $redirect['path'] = preg_replace('|/+|', '/', $redirect['path']);
 370
 371         // Always trailing slash the Front Page URL
 372         if ( trailingslashit( $redirect['path'] ) == trailingslashit( $user_home['path'] ) )
 373                 $redirect['path'] = trailingslashit($redirect['path']);
 374
 375         // Ignore differences in host capitalization, as this can lead to infinite redirects
 376         // Only redirect no-www <=> yes-www
 377         if ( strtolower($original['host']) == strtolower($redirect['host']) ||
 378                 ( strtolower($original['host']) != 'www.' . strtolower($redirect['host']) && 'www.' . strtolower($original['host']) != strtolower($redirect['host']) ) )
 379                 $redirect['host'] = $original['host'];
 380
 381         $compare_original = array($original['host'], $original['path']);
 382
 383         if ( !empty( $original['port'] ) )
 384                 $compare_original[] = $original['port'];
 385
 386         if ( !empty( $original['query'] ) )
 387                 $compare_original[] = $original['query'];
 388
 389         $compare_redirect = array($redirect['host'], $redirect['path']);
 390
 391         if ( !empty( $redirect['port'] ) )
 392                 $compare_redirect[] = $redirect['port'];
 393
 394         if ( !empty( $redirect['query'] ) )
 395                 $compare_redirect[] = $redirect['query'];
 396
 397         if ( $compare_original !== $compare_redirect ) {
 398                 $redirect_url = $redirect['scheme'] . '://' . $redirect['host'];
 399                 if ( !empty($redirect['port']) )
 400                         $redirect_url .= ':' . $redirect['port'];
 401                 $redirect_url .= $redirect['path'];
 402                 if ( !empty($redirect['query']) )
 403                         $redirect_url .= '?' . $redirect['query'];
 404         }
 405
 406         if ( !$redirect_url || $redirect_url == $requested_url )
 407                 return false;
 408
 409         // Hex encoded octets are case-insensitive.
 410         if ( false !== strpos($requested_url, '%') ) {
 411                 if ( !function_exists('lowercase_octets') ) {
 412                         function lowercase_octets($matches) {
 413                                 return strtolower( $matches[0] );
 414                         }
 415                 }
 416                 $requested_url = preg_replace_callback('|%[a-fA-F0-9][a-fA-F0-9]|', 'lowercase_octets', $requested_url);
 417         }
 418
 419         // Note that you can use the "redirect_canonical" filter to cancel a canonical redirect for whatever reason by returning false
 420         $redirect_url = apply_filters('redirect_canonical', $redirect_url, $requested_url);
 421
 422         if ( !$redirect_url || $redirect_url == $requested_url ) // yes, again -- in case the filter aborted the request
 423                 return false;
 424
 425         if ( $do_redirect ) {
 426                 // protect against chained redirects
 427                 if ( !redirect_canonical($redirect_url, false) ) {
 428                         wp_redirect($redirect_url, 301);
 429                         exit();
 430                 } else {
 431                         // Debug
 432                         // die("1: $redirect_url<br />2: " . redirect_canonical( $redirect_url, false ) );
 433                         return false;
 434                 }
 435         } else {
 436                 return $redirect_url;
 437         }
 438 }
 439
 440 /**
 441  * Removes arguments from a query string if they are not present in a URL
 442  * DO NOT use this in plugin code.
 443  *
 444  * @since 3.4
 445  * @access private
 446  *
 447  * @return string The altered query string
 448  */
 449 function _remove_qs_args_if_not_in_url( $query_string, Array $args_to_check, $url ) {
 450         $parsed_url = @parse_url( $url );
 451         if ( ! empty( $parsed_url['query'] ) ) {
 452                 parse_str( $parsed_url['query'], $parsed_query );
 453                 foreach ( $args_to_check as $qv ) {
 454                         if ( !isset( $parsed_query[$qv] ) )
 455                                 $query_string = remove_query_arg( $qv, $query_string );
 456                 }
 457         } else {
 458                 $query_string = remove_query_arg( $args_to_check, $query_string );
 459         }
 460         return $query_string;
 461 }
 462
 463 /**
 464  * Attempts to guess the correct URL based on query vars
 465  *
 466  * @since 2.3.0
 467  * @uses $wpdb
 468  *
 469  * @return bool|string The correct URL if one is found. False on failure.
 470  */
 471 function redirect_guess_404_permalink() {
 472         global $wpdb, $wp_rewrite;
 473
 474         if ( get_query_var('name') ) {
 475                 $where = $wpdb->prepare("post_name LIKE %s", like_escape( get_query_var('name') ) . '%');
 476
 477                 // if any of post_type, year, monthnum, or day are set, use them to refine the query
 478                 if ( get_query_var('post_type') )
 479                         $where .= $wpdb->prepare(" AND post_type = %s", get_query_var('post_type'));
 480                 else
 481                         $where .= " AND post_type IN ('" . implode( "', '", get_post_types( array( 'public' => true ) ) ) . "')";
 482
 483                 if ( get_query_var('year') )
 484                         $where .= $wpdb->prepare(" AND YEAR(post_date) = %d", get_query_var('year'));
 485                 if ( get_query_var('monthnum') )
 486                         $where .= $wpdb->prepare(" AND MONTH(post_date) = %d", get_query_var('monthnum'));
 487                 if ( get_query_var('day') )
 488                         $where .= $wpdb->prepare(" AND DAYOFMONTH(post_date) = %d", get_query_var('day'));
 489
 490                 $post_id = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE $where AND post_status = 'publish'");
 491                 if ( ! $post_id )
 492                         return false;
 493                 if ( get_query_var( 'feed' ) )
 494                         return get_post_comments_feed_link( $post_id, get_query_var( 'feed' ) );
 495                 elseif ( get_query_var( 'page' ) )
 496                         return trailingslashit( get_permalink( $post_id ) ) . user_trailingslashit( get_query_var( 'page' ), 'single_paged' );
 497                 else
 498                         return get_permalink( $post_id );
 499         }
 500
 501         return false;
 502 }
 503
 504 add_action('template_redirect', 'redirect_canonical');
 505
 506 function wp_redirect_admin_locations() {
 507         global $wp_rewrite;
 508         if ( ! ( is_404() && $wp_rewrite->using_permalinks() ) )
 509                 return;
 510
 511         $admins = array(
 512                 home_url( 'wp-admin', 'relative' ),
 513                 home_url( 'dashboard', 'relative' ),
 514                 home_url( 'admin', 'relative' ),
 515                 site_url( 'dashboard', 'relative' ),
 516                 site_url( 'admin', 'relative' ),
 517         );
 518         if ( in_array( untrailingslashit( $_SERVER['REQUEST_URI'] ), $admins ) ) {
 519                 wp_redirect( admin_url() );
 520                 exit;
 521         }
 522
 523         $logins = array(
 524                 home_url( 'wp-login.php', 'relative' ),
 525                 home_url( 'login', 'relative' ),
 526                 site_url( 'login', 'relative' ),
 527         );
 528         if ( in_array( untrailingslashit( $_SERVER['REQUEST_URI'] ), $logins ) ) {
 529                 wp_redirect( site_url( 'wp-login.php', 'login' ) );
 530                 exit;
 531         }
 532 }
 533
 534 add_action( 'template_redirect', 'wp_redirect_admin_locations', 1000 );