WordPress 3.4
[autoinstalls/wordpress.git] / 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( $requested_url ) ) {
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 from the current URL (that produced a 404) or
465  * the current query variables.
466  *
467  * @since 2.3.0
468  * @uses $wpdb
469  *
470  * @param string $current_url Optional. The URL that has 404'd.
471  * @return bool|string The correct URL if one is found. False on failure.
472  */
473 function redirect_guess_404_permalink( $current_url = '' ) {
474         global $wpdb, $wp_rewrite;
475
476         if ( ! empty( $current_url ) )
477                 $parsed_url = @parse_url( $current_url );
478
479         // Attempt to redirect bare category slugs if the permalink structure starts
480         // with the %category% tag.
481         if ( isset( $parsed_url['path'] )
482                 && preg_match( '#^[^%]+%category%#', $wp_rewrite->permalink_structure )
483                 && $cat = get_category_by_path( $parsed_url['path'] )
484         ) {
485                 if ( ! is_wp_error( $cat ) )
486                         return get_term_link( $cat );
487         }
488
489         if ( get_query_var('name') ) {
490                 $where = $wpdb->prepare("post_name LIKE %s", like_escape( get_query_var('name') ) . '%');
491
492                 // if any of post_type, year, monthnum, or day are set, use them to refine the query
493                 if ( get_query_var('post_type') )
494                         $where .= $wpdb->prepare(" AND post_type = %s", get_query_var('post_type'));
495                 else
496                         $where .= " AND post_type IN ('" . implode( "', '", get_post_types( array( 'public' => true ) ) ) . "')";
497
498                 if ( get_query_var('year') )
499                         $where .= $wpdb->prepare(" AND YEAR(post_date) = %d", get_query_var('year'));
500                 if ( get_query_var('monthnum') )
501                         $where .= $wpdb->prepare(" AND MONTH(post_date) = %d", get_query_var('monthnum'));
502                 if ( get_query_var('day') )
503                         $where .= $wpdb->prepare(" AND DAYOFMONTH(post_date) = %d", get_query_var('day'));
504
505                 $post_id = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE $where AND post_status = 'publish'");
506                 if ( ! $post_id )
507                         return false;
508                 if ( get_query_var( 'feed' ) )
509                         return get_post_comments_feed_link( $post_id, get_query_var( 'feed' ) );
510                 elseif ( get_query_var( 'page' ) )
511                         return trailingslashit( get_permalink( $post_id ) ) . user_trailingslashit( get_query_var( 'page' ), 'single_paged' );
512                 else
513                         return get_permalink( $post_id );
514         }
515
516         return false;
517 }
518
519 add_action('template_redirect', 'redirect_canonical');
520
521 function wp_redirect_admin_locations() {
522         global $wp_rewrite;
523         if ( ! ( is_404() && $wp_rewrite->using_permalinks() ) )
524                 return;
525
526         $admins = array(
527                 home_url( 'wp-admin', 'relative' ),
528                 home_url( 'dashboard', 'relative' ),
529                 home_url( 'admin', 'relative' ),
530                 site_url( 'dashboard', 'relative' ),
531                 site_url( 'admin', 'relative' ),
532         );
533         if ( in_array( untrailingslashit( $_SERVER['REQUEST_URI'] ), $admins ) ) {
534                 wp_redirect( admin_url() );
535                 exit;
536         }
537
538         $logins = array(
539                 home_url( 'wp-login.php', 'relative' ),
540                 home_url( 'login', 'relative' ),
541                 site_url( 'login', 'relative' ),
542         );
543         if ( in_array( untrailingslashit( $_SERVER['REQUEST_URI'] ), $logins ) ) {
544                 wp_redirect( site_url( 'wp-login.php', 'login' ) );
545                 exit;
546         }
547 }
548
549 add_action( 'template_redirect', 'wp_redirect_admin_locations', 1000 );