* Canonical API to handle WordPress Redirecting
* Based on "Permalink Redirect" from Scott Yang and "Enforce www. Preference"
* Redirects incoming links to the proper URL based on the site url.
* Search engines consider www.somedomain.com and somedomain.com to be two
* different URLs when they both go to the same location. This SEO enhancement
* prevents penalty for duplicate content by redirecting all incoming links to
* Prevents redirection for feeds, trackbacks, searches, and
* admin URLs. Does not redirect on non-pretty-permalink-supporting IIS 7+,
* page/post previews, WP admin, Trackbacks, robots.txt, favicon.ico, searches,
* Will also attempt to find the correct link when a user enters a URL that does
* not exist based on exact WordPress query. Will instead try to parse the URL
* or query in an attempt to figure the correct page to go to.
* @global WP_Rewrite $wp_rewrite WordPress rewrite component.
* @global WP_Query $wp_query WordPress Query object.
* @global wpdb $wpdb WordPress database abstraction object.
* @global WP $wp Current WordPress environment instance.
* @param string $requested_url Optional. The URL that was requested, used to
* figure if redirect is needed.
* @param bool $do_redirect Optional. Redirect to the new URL.
* @return string|void The string of the URL, if redirect needed.
function redirect_canonical( $requested_url = null, $do_redirect = true ) {
global $wp_rewrite, $is_IIS, $wp_query, $wpdb, $wp;
if ( isset( $_SERVER['REQUEST_METHOD'] ) && ! in_array( strtoupper( $_SERVER['REQUEST_METHOD'] ), array( 'GET', 'HEAD' ), true ) ) {
// If we're not in wp-admin and the post has been published and preview nonce
// is non-existent or invalid then no need for preview in query.
if ( is_preview() && get_query_var( 'p' ) && 'publish' === get_post_status( get_query_var( 'p' ) ) ) {
if ( ! isset( $_GET['preview_id'] )
|| ! isset( $_GET['preview_nonce'] )
|| ! wp_verify_nonce( $_GET['preview_nonce'], 'post_preview_' . (int) $_GET['preview_id'] )
$wp_query->is_preview = false;
if ( is_admin() || is_search() || is_preview() || is_trackback() || is_favicon()
|| ( $is_IIS && ! iis7_supports_permalinks() )
if ( ! $requested_url && isset( $_SERVER['HTTP_HOST'] ) ) {
// Build the URL in the address bar.
$requested_url = is_ssl() ? 'https://' : 'http://';
$requested_url .= $_SERVER['HTTP_HOST'];
$requested_url .= $_SERVER['REQUEST_URI'];
$original = parse_url( $requested_url );
if ( false === $original ) {
if ( ! isset( $redirect['path'] ) ) {
if ( ! isset( $redirect['query'] ) ) {
* If the original URL ended with non-breaking spaces, they were almost
* certainly inserted by accident. Let's remove them, so the reader doesn't
* see a 404 error with no obvious cause.
$redirect['path'] = preg_replace( '|(%C2%A0)+$|i', '', $redirect['path'] );
// It's not a preview, so remove it from URL.
if ( get_query_var( 'preview' ) ) {
$redirect['query'] = remove_query_arg( 'preview', $redirect['query'] );
$post_id = get_query_var( 'p' );
if ( is_feed() && $post_id ) {
$redirect_url = get_post_comments_feed_link( $post_id, get_query_var( 'feed' ) );
$redirect_obj = get_post( $post_id );
$redirect['query'] = _remove_qs_args_if_not_in_url(
array( 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type', 'feed' ),
$redirect['path'] = parse_url( $redirect_url, PHP_URL_PATH );
if ( is_singular() && $wp_query->post_count < 1 && $post_id ) {
$vars = $wpdb->get_results( $wpdb->prepare( "SELECT post_type, post_parent FROM $wpdb->posts WHERE ID = %d", $post_id ) );
if ( ! empty( $vars[0] ) ) {
if ( 'revision' === $vars->post_type && $vars->post_parent > 0 ) {
$post_id = $vars->post_parent;
$redirect_url = get_permalink( $post_id );
$redirect_obj = get_post( $post_id );
$redirect['query'] = _remove_qs_args_if_not_in_url(
array( 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type' ),
// These tests give us a WP-generated permalink.
// Redirect ?page_id, ?p=, ?attachment_id= to their respective URLs.
$post_id = max( get_query_var( 'p' ), get_query_var( 'page_id' ), get_query_var( 'attachment_id' ) );
$redirect_post = $post_id ? get_post( $post_id ) : false;
$post_type_obj = get_post_type_object( $redirect_post->post_type );
if ( $post_type_obj && $post_type_obj->public && 'auto-draft' !== $redirect_post->post_status ) {
$redirect_url = get_permalink( $redirect_post );
$redirect_obj = get_post( $redirect_post );
$redirect['query'] = _remove_qs_args_if_not_in_url(
array( 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type' ),
$year = get_query_var( 'year' );
$month = get_query_var( 'monthnum' );
$day = get_query_var( 'day' );
if ( $year && $month && $day ) {
$date = sprintf( '%04d-%02d-%02d', $year, $month, $day );
if ( ! wp_checkdate( $month, $day, $year, $date ) ) {
$redirect_url = get_month_link( $year, $month );
$redirect['query'] = _remove_qs_args_if_not_in_url(
array( 'year', 'monthnum', 'day' ),
} elseif ( $year && $month && $month > 12 ) {
$redirect_url = get_year_link( $year );
$redirect['query'] = _remove_qs_args_if_not_in_url(
array( 'year', 'monthnum' ),
// Strip off non-existing <!--nextpage--> links from single posts or pages.
if ( get_query_var( 'page' ) ) {
if ( $wp_query->queried_object instanceof WP_Post ) {
$post_id = $wp_query->queried_object->ID;
} elseif ( $wp_query->post ) {
$post_id = $wp_query->post->ID;
$redirect_url = get_permalink( $post_id );
$redirect_obj = get_post( $post_id );
$redirect['path'] = rtrim( $redirect['path'], (int) get_query_var( 'page' ) . '/' );
$redirect['query'] = remove_query_arg( 'page', $redirect['query'] );
$redirect_url = redirect_guess_404_permalink();
$redirect['query'] = _remove_qs_args_if_not_in_url(
array( 'page', 'feed', 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type' ),
} elseif ( is_object( $wp_rewrite ) && $wp_rewrite->using_permalinks() ) {
// Rewriting of old ?p=X, ?m=2004, ?m=200401, ?m=20040101.
&& ! array_diff( array_keys( $wp->query_vars ), array( 'attachment', 'attachment_id' ) )
if ( ! empty( $_GET['attachment_id'] ) ) {
$redirect_url = get_attachment_link( get_query_var( 'attachment_id' ) );
$redirect_obj = get_post( get_query_var( 'attachment_id' ) );
$redirect['query'] = remove_query_arg( 'attachment_id', $redirect['query'] );
$redirect_url = get_attachment_link();
$redirect_obj = get_post();
} elseif ( is_single() && ! empty( $_GET['p'] ) && ! $redirect_url ) {
$redirect_url = get_permalink( get_query_var( 'p' ) );
$redirect_obj = get_post( get_query_var( 'p' ) );
$redirect['query'] = remove_query_arg( array( 'p', 'post_type' ), $redirect['query'] );
} elseif ( is_single() && ! empty( $_GET['name'] ) && ! $redirect_url ) {
$redirect_url = get_permalink( $wp_query->get_queried_object_id() );
$redirect_obj = get_post( $wp_query->get_queried_object_id() );
$redirect['query'] = remove_query_arg( 'name', $redirect['query'] );
} elseif ( is_page() && ! empty( $_GET['page_id'] ) && ! $redirect_url ) {
$redirect_url = get_permalink( get_query_var( 'page_id' ) );
$redirect_obj = get_post( get_query_var( 'page_id' ) );
$redirect['query'] = remove_query_arg( 'page_id', $redirect['query'] );
} elseif ( is_page() && ! is_feed() && ! $redirect_url
&& 'page' === get_option( 'show_on_front' ) && get_queried_object_id() === (int) get_option( 'page_on_front' )
$redirect_url = home_url( '/' );
} elseif ( is_home() && ! empty( $_GET['page_id'] ) && ! $redirect_url
&& 'page' === get_option( 'show_on_front' ) && get_query_var( 'page_id' ) === (int) get_option( 'page_for_posts' )
$redirect_url = get_permalink( get_option( 'page_for_posts' ) );
$redirect_obj = get_post( get_option( 'page_for_posts' ) );
$redirect['query'] = remove_query_arg( 'page_id', $redirect['query'] );
} elseif ( ! empty( $_GET['m'] ) && ( is_year() || is_month() || is_day() ) ) {
$m = get_query_var( 'm' );
switch ( strlen( $m ) ) {
$redirect_url = get_year_link( $m );
$redirect_url = get_month_link( substr( $m, 0, 4 ), substr( $m, 4, 2 ) );
$redirect_url = get_day_link( substr( $m, 0, 4 ), substr( $m, 4, 2 ), substr( $m, 6, 2 ) );
$redirect['query'] = remove_query_arg( 'm', $redirect['query'] );
// Now moving on to non ?m=X year/month/day links.
$year = get_query_var( 'year' );
$month = get_query_var( 'monthnum' );
$day = get_query_var( 'day' );
if ( is_day() && $year && $month && ! empty( $_GET['day'] ) ) {
$redirect_url = get_day_link( $year, $month, $day );
$redirect['query'] = remove_query_arg( array( 'year', 'monthnum', 'day' ), $redirect['query'] );
} elseif ( is_month() && $year && ! empty( $_GET['monthnum'] ) ) {
$redirect_url = get_month_link( $year, $month );
$redirect['query'] = remove_query_arg( array( 'year', 'monthnum' ), $redirect['query'] );
} elseif ( is_year() && ! empty( $_GET['year'] ) ) {
$redirect_url = get_year_link( $year );
$redirect['query'] = remove_query_arg( 'year', $redirect['query'] );
} elseif ( is_author() && ! empty( $_GET['author'] ) && preg_match( '|^[0-9]+$|', $_GET['author'] ) ) {
$author = get_userdata( get_query_var( '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 ) )
$redirect_url = get_author_posts_url( $author->ID, $author->user_nicename );
$redirect['query'] = remove_query_arg( 'author', $redirect['query'] );
} elseif ( is_category() || is_tag() || is_tax() ) { // Terms (tags/categories).
foreach ( $wp_query->tax_query->queried_terms as $tax_query ) {
$term_count += count( $tax_query['terms'] );
$obj = $wp_query->get_queried_object();
if ( $term_count <= 1 && ! empty( $obj->term_id ) ) {
$tax_url = get_term_link( (int) $obj->term_id, $obj->taxonomy );
if ( $tax_url && ! is_wp_error( $tax_url ) ) {
if ( ! empty( $redirect['query'] ) ) {
// Strip taxonomy query vars off the URL.
$qv_remove = array( 'term', 'taxonomy' );
$qv_remove[] = 'category_name';
// Custom taxonomies will have a custom query var, remove those too.
$tax_obj = get_taxonomy( $obj->taxonomy );
if ( false !== $tax_obj->query_var ) {
$qv_remove[] = $tax_obj->query_var;
$rewrite_vars = array_diff( array_keys( $wp_query->query ), array_keys( $_GET ) );
// Check to see if all the query vars are coming from the rewrite, none are set via $_GET.
if ( ! array_diff( $rewrite_vars, array_keys( $_GET ) ) ) {
// Remove all of the per-tax query vars.
$redirect['query'] = remove_query_arg( $qv_remove, $redirect['query'] );
// Create the destination URL for this taxonomy.
$tax_url = parse_url( $tax_url );
if ( ! empty( $tax_url['query'] ) ) {
// Taxonomy accessible via ?taxonomy=...&term=... or any custom query var.
parse_str( $tax_url['query'], $query_vars );
$redirect['query'] = add_query_arg( $query_vars, $redirect['query'] );
// Taxonomy is accessible via a "pretty URL".
$redirect['path'] = $tax_url['path'];
// Some query vars are set via $_GET. Unset those from $_GET that exist via the rewrite.
foreach ( $qv_remove as $_qv ) {
if ( isset( $rewrite_vars[ $_qv ] ) ) {
$redirect['query'] = remove_query_arg( $_qv, $redirect['query'] );
} elseif ( is_single() && strpos( $wp_rewrite->permalink_structure, '%category%' ) !== false ) {
$category_name = get_query_var( 'category_name' );
$category = get_category_by_path( $category_name );
if ( ! $category || is_wp_error( $category )
|| ! has_term( $category->term_id, 'category', $wp_query->get_queried_object_id() )
$redirect_url = get_permalink( $wp_query->get_queried_object_id() );
$redirect_obj = get_post( $wp_query->get_queried_object_id() );
if ( is_singular() && get_query_var( 'page' ) ) {
$page = get_query_var( 'page' );
$redirect_url = get_permalink( get_queried_object_id() );
$redirect_obj = get_post( get_queried_object_id() );
$redirect_url = trailingslashit( $redirect_url );
$redirect_url .= user_trailingslashit( "$wp_rewrite->pagination_base/$page", 'paged' );
$redirect_url .= user_trailingslashit( $page, 'single_paged' );
$redirect['query'] = remove_query_arg( 'page', $redirect['query'] );
if ( get_query_var( 'sitemap' ) ) {
$redirect_url = get_sitemap_url( get_query_var( 'sitemap' ), get_query_var( 'sitemap-subtype' ), get_query_var( 'paged' ) );
$redirect['query'] = remove_query_arg( array( 'sitemap', 'sitemap-subtype', 'paged' ), $redirect['query'] );
} elseif ( get_query_var( 'paged' ) || is_feed() || get_query_var( 'cpage' ) ) {
$paged = get_query_var( 'paged' );
$feed = get_query_var( 'feed' );
$cpage = get_query_var( 'cpage' );
while ( preg_match( "#/$wp_rewrite->pagination_base/?[0-9]+?(/+)?$#", $redirect['path'] )
|| preg_match( '#/(comments/?)?(feed|rss2?|rdf|atom)(/+)?$#', $redirect['path'] )
|| preg_match( "#/{$wp_rewrite->comments_pagination_base}-[0-9]+(/+)?$#", $redirect['path'] )
// Strip off any existing paging.
$redirect['path'] = preg_replace( "#/$wp_rewrite->pagination_base/?[0-9]+?(/+)?$#", '/', $redirect['path'] );
// Strip off feed endings.
$redirect['path'] = preg_replace( '#/(comments/?)?(feed|rss2?|rdf|atom)(/+|$)#', '/', $redirect['path'] );
// Strip off any existing comment paging.
$redirect['path'] = preg_replace( "#/{$wp_rewrite->comments_pagination_base}-[0-9]+?(/+)?$#", '/', $redirect['path'] );
$default_feed = get_default_feed();
if ( is_feed() && in_array( $feed, $wp_rewrite->feeds, true ) ) {
$addl_path = ! empty( $addl_path ) ? trailingslashit( $addl_path ) : '';
if ( ! is_singular() && get_query_var( 'withcomments' ) ) {
$addl_path .= 'comments/';
if ( ( 'rss' === $default_feed && 'feed' === $feed ) || 'rss' === $feed ) {
$format = ( 'rss2' === $default_feed ) ? '' : 'rss2';
$format = ( $default_feed === $feed || 'feed' === $feed ) ? '' : $feed;
$addl_path .= user_trailingslashit( 'feed/' . $format, 'feed' );
$redirect['query'] = remove_query_arg( 'feed', $redirect['query'] );
} elseif ( is_feed() && 'old' === $feed ) {
'wp-commentsrss2.php' => 'comments_rss2',
'wp-feed.php' => $default_feed,
if ( isset( $old_feed_files[ basename( $redirect['path'] ) ] ) ) {
$redirect_url = get_feed_link( $old_feed_files[ basename( $redirect['path'] ) ] );
wp_redirect( $redirect_url, 301 );
$redirect['query'] = remove_query_arg( 'paged', $redirect['query'] );
$addl_path = ! empty( $addl_path ) ? trailingslashit( $addl_path ) : '';
$addl_path .= user_trailingslashit( "$wp_rewrite->pagination_base/$paged", 'paged' );
} elseif ( $paged > 1 ) {
$redirect['query'] = add_query_arg( 'paged', $paged, $redirect['query'] );