WordPress开发者和主题制作者的搜索引擎



redirect_canonical ›

Since2.3.0
已弃用n/a
redirect_canonical ( $requested_url = null, $do_redirect = true )
参数: (2)
  • (string) $requested_url Optional. The URL that was requested, used to figure if redirect is needed.
    Required: No
    默认: null
  • (bool) $do_redirect Optional. Redirect to the new URL.
    Required: No
    默认: true
返回:
  • (string|void) The string of the URL, if redirect needed.
定义在:
文档:

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 one or the other.

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, searches, or on POST requests.

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.



源码

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' ) ) ) {
		return;
	}

	// 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_trackback() || is_search() || is_admin() || is_preview() || is_robots() || ( $is_IIS && !iis7_supports_permalinks() ) ) {
		return;
	}

	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 ) {
		return;
	}

	$redirect = $original;
	$redirect_url = false;

	// Notice fixing
	if ( !isset($redirect['path']) )
		$redirect['path'] = '';
	if ( !isset($redirect['query']) )
		$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'] );
	}

	if ( is_feed() && ( $id = get_query_var( 'p' ) ) ) {
		if ( $redirect_url = get_post_comments_feed_link( $id, get_query_var( 'feed' ) ) ) {
			$redirect['query'] = _remove_qs_args_if_not_in_url( $redirect['query'], array( 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type', 'feed'), $redirect_url );
			$redirect['path'] = parse_url( $redirect_url, PHP_URL_PATH );
		}
	}

	if ( is_singular() && 1 > $wp_query->post_count && ($id = get_query_var('p')) ) {

		$vars = $wpdb->get_results( $wpdb->prepare("SELECT post_type, post_parent FROM $wpdb->posts WHERE ID = %d", $id) );

		if ( isset($vars[0]) && $vars = $vars[0] ) {
			if ( 'revision' == $vars->post_type && $vars->post_parent > 0 )
				$id = $vars->post_parent;

			if ( $redirect_url = get_permalink($id) )
				$redirect['query'] = _remove_qs_args_if_not_in_url( $redirect['query'], array( 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type' ), $redirect_url );
		}
	}

	// These tests give us a WP-generated permalink
	if ( is_404() ) {

		// Redirect ?page_id, ?p=, ?attachment_id= to their respective url's
		$id = max( get_query_var('p'), get_query_var('page_id'), get_query_var('attachment_id') );
		if ( $id && $redirect_post = get_post($id) ) {
			$post_type_obj = get_post_type_object($redirect_post->post_type);
			if ( $post_type_obj->public && 'auto-draft' != $redirect_post->post_status ) {
				$redirect_url = get_permalink($redirect_post);
				$redirect['query'] = _remove_qs_args_if_not_in_url( $redirect['query'], array( 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type' ), $redirect_url );
			}
		}

		if ( get_query_var( 'day' ) && get_query_var( 'monthnum' ) && get_query_var( 'year' ) ) {
			$year  = get_query_var( 'year' );
			$month = get_query_var( 'monthnum' );
			$day   = get_query_var( '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( $redirect['query'], array( 'year', 'monthnum', 'day' ), $redirect_url );
			}
		} elseif ( get_query_var( 'monthnum' ) && get_query_var( 'year' ) && 12 < get_query_var( 'monthnum' ) ) {
			$redirect_url = get_year_link( get_query_var( 'year' ) );
			$redirect['query'] = _remove_qs_args_if_not_in_url( $redirect['query'], array( 'year', 'monthnum' ), $redirect_url );
		}

		if ( ! $redirect_url ) {
			if ( $redirect_url = redirect_guess_404_permalink() ) {
				$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 );
			}
		}

		if ( get_query_var( 'page' ) && $wp_query->post &&
			false !== strpos( $wp_query->post->post_content, '<!--nextpage-->' ) ) {
			$redirect['path'] = rtrim( $redirect['path'], (int) get_query_var( 'page' ) . '/' );
			$redirect['query'] = remove_query_arg( 'page', $redirect['query'] );
			$redirect_url = get_permalink( $wp_query->post->ID );
		}

	} elseif ( is_object($wp_rewrite) && $wp_rewrite->using_permalinks() ) {
		// rewriting of old ?p=X, ?m=2004, ?m=200401, ?m=20040101
		if ( is_attachment() &&
			! array_diff( array_keys( $wp->query_vars ), array( 'attachment', 'attachment_id' ) ) &&
			! $redirect_url ) {
			if ( ! empty( $_GET['attachment_id'] ) ) {
				$redirect_url = get_attachment_link( get_query_var( 'attachment_id' ) );
				if ( $redirect_url ) {
					$redirect['query'] = remove_query_arg( 'attachment_id', $redirect['query'] );
				}
			} else {
				$redirect_url = get_attachment_link();
			}
		} elseif ( is_single() && !empty($_GET['p']) && ! $redirect_url ) {
			if ( $redirect_url = get_permalink(get_query_var('p')) )
				$redirect['query'] = remove_query_arg(array('p', 'post_type'), $redirect['query']);
		} elseif ( is_single() && !empty($_GET['name'])  && ! $redirect_url ) {
			if ( $redirect_url = get_permalink( $wp_query->get_queried_object_id() ) )
				$redirect['query'] = remove_query_arg('name', $redirect['query']);
		} elseif ( is_page() && !empty($_GET['page_id']) && ! $redirect_url ) {
			if ( $redirect_url = get_permalink(get_query_var('page_id')) )
				$redirect['query'] = remove_query_arg('page_id', $redirect['query']);
		} elseif ( is_page() && !is_feed() && 'page' == get_option('show_on_front') && get_queried_object_id() == get_option('page_on_front')  && ! $redirect_url ) {
			$redirect_url = home_url('/');
		} elseif ( is_home() && !empty($_GET['page_id']) && 'page' == get_option('show_on_front') && get_query_var('page_id') == get_option('page_for_posts')  && ! $redirect_url ) {
			if ( $redirect_url = get_permalink(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) ) {
				case 4: // Yearly
					$redirect_url = get_year_link($m);
					break;
				case 6: // Monthly
					$redirect_url = get_month_link( substr($m, 0, 4), substr($m, 4, 2) );
					break;
				case 8: // Daily
					$redirect_url = get_day_link(substr($m, 0, 4), substr($m, 4, 2), substr($m, 6, 2));
					break;
			}
			if ( $redirect_url )
				$redirect['query'] = remove_query_arg('m', $redirect['query']);
		// now moving on to non ?m=X year/month/day links
		} elseif ( is_day() && get_query_var('year') && get_query_var('monthnum') && !empty($_GET['day']) ) {
			if ( $redirect_url = get_day_link(get_query_var('year'), get_query_var('monthnum'), get_query_var('day')) )
				$redirect['query'] = remove_query_arg(array('year', 'monthnum', 'day'), $redirect['query']);
		} elseif ( is_month() && get_query_var('year') && !empty($_GET['monthnum']) ) {
			if ( $redirect_url = get_month_link(get_query_var('year'), get_query_var('monthnum')) )
				$redirect['query'] = remove_query_arg(array('year', 'monthnum'), $redirect['query']);
		} elseif ( is_year() && !empty($_GET['year']) ) {
			if ( $redirect_url = get_year_link(get_query_var('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'));
			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 ) ) ) {
				if ( $redirect_url = get_author_posts_url($author->ID, $author->user_nicename) )
					$redirect['query'] = remove_query_arg('author', $redirect['query']);
			}
		} elseif ( is_category() || is_tag() || is_tax() ) { // Terms (Tags/categories)

			$term_count = 0;
			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, $obj->taxonomy) ) && !is_wp_error($tax_url) ) {
				if ( !empty($redirect['query']) ) {
					// Strip taxonomy query vars off the url.
					$qv_remove = array( 'term', 'taxonomy');
					if ( is_category() ) {
						$qv_remove[] = 'category_name';
						$qv_remove[] = 'cat';
					} elseif ( is_tag() ) {
						$qv_remove[] = 'tag';
						$qv_remove[] = 'tag_id';
					} else { // 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) );

					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
						$redirect['query'] = remove_query_arg($qv_remove, $redirect['query']); //Remove all of the per-tax qv's

						// Create the destination url for this taxonomy
						$tax_url = parse_url($tax_url);
						if ( ! empty($tax_url['query']) ) { // Taxonomy accessible via ?taxonomy=..&term=.. or any custom qv..
							parse_str($tax_url['query'], $query_vars);
							$redirect['query'] = add_query_arg($query_vars, $redirect['query']);
						} else { // Taxonomy is accessible via a "pretty-URL"
							$redirect['path'] = $tax_url['path'];
						}

					} else { // 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 && $cat = get_query_var( 'category_name' ) ) {
			$category = get_category_by_path( $cat );
			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());
			}
		}

		// Post Paging
		if ( is_singular() && get_query_var('page') ) {
			if ( !$redirect_url )
				$redirect_url = get_permalink( get_queried_object_id() );

			$page = get_query_var( 'page' );
			if ( $page > 1 ) {
				if ( is_front_page() ) {
					$redirect_url = trailingslashit( $redirect_url ) . user_trailingslashit( "$wp_rewrite->pagination_base/$page", 'paged' );
				} else {
					$redirect_url = trailingslashit( $redirect_url ) . user_trailingslashit( $page, 'single_paged' );
				}
			}
			$redirect['query'] = remove_query_arg( 'page', $redirect['query'] );
		}

		// paging and feeds
		if ( get_query_var('paged') || is_feed() || get_query_var('cpage') ) {
			while ( preg_match( "#/$wp_rewrite->pagination_base/?[0-9]+?(/+)?$#", $redirect['path'] ) || preg_match( '#/(comments/?)?(feed|rss|rdf|atom|rss2)(/+)?$#', $redirect['path'] ) || preg_match( "#/{$wp_rewrite->comments_pagination_base}-[0-9]+(/+)?$#", $redirect['path'] ) ) {
				// Strip off paging and feed
				$redirect['path'] = preg_replace("#/$wp_rewrite->pagination_base/?[0-9]+?(/+)?$#", '/', $redirect['path']); // strip off any existing paging
				$redirect['path'] = preg_replace('#/(comments/?)?(feed|rss2?|rdf|atom)(/+|$)#', '/', $redirect['path']); // strip off feed endings
				$redirect['path'] = preg_replace("#/{$wp_rewrite->comments_pagination_base}-[0-9]+?(/+)?$#", '/', $redirect['path']); // strip off any existing comment paging
			}

			$addl_path = '';
			if ( is_feed() && in_array( get_query_var('feed'), $wp_rewrite->feeds ) ) {
				$addl_path = !empty( $addl_path ) ? trailingslashit($addl_path) : '';
				if ( !is_singular() && get_query_var( 'withcomments' ) )
					$addl_path .= 'comments/';
				if ( ( 'rss' == get_default_feed() && 'feed' == get_query_var('feed') ) || 'rss' == get_query_var('feed') )
					$addl_path .= user_trailingslashit( 'feed/' . ( ( get_default_feed() == 'rss2' ) ? '' : 'rss2' ), 'feed' );
				else
					$addl_path .= user_trailingslashit( 'feed/' . ( ( get_default_feed() ==  get_query_var('feed') || 'feed' == get_query_var('feed') ) ? '' : get_query_var('feed') ), 'feed' );
				$redirect['query'] = remove_query_arg( 'feed', $redirect['query'] );
			} elseif ( is_feed() && 'old' == get_query_var('feed') ) {
				$old_feed_files = array(
					'wp-atom.php'         => 'atom',
					'wp-commentsrss2.php' => 'comments_rss2',
					'wp-feed.php'         => get_default_feed(),
					'wp-rdf.php'          => 'rdf',
					'wp-rss.php'          => 'rss2',
					'wp-rss2.php'         => 'rss2',
				);
				if ( isset( $old_feed_files[ basename( $redirect['path'] ) ] ) ) {
					$redirect_url = get_feed_link( $old_feed_files[ basename( $redirect['path'] ) ] );
					wp_redirect( $redirect_url, 301 );
					die();
				}
			}

			if ( get_query_var('paged') > 0 ) {
				$paged = get_query_var('paged');
				$redirect['query'] = remove_query_arg( 'paged', $redirect['query'] );
				if ( !is_feed() ) {
					if ( $paged > 1 && !is_single() ) {
						$addl_path = ( !empty( $addl_path ) ? trailingslashit($addl_path) : '' ) . user_trailingslashit("$wp_rewrite->pagination_base/$paged", 'paged');
					} elseif ( !is_single() ) {
						$addl_path = !empty( $addl_path ) ? trailingslashit($addl_path) : '';
					}
				} elseif ( $paged > 1 ) {
					$redirect['query'] = add_query_arg( 'paged', $paged, $redirect['query'] );
				}
			}

			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 )
			) ) {
				$addl_path = ( !empty( $addl_path ) ? trailingslashit($addl_path) : '' ) . user_trailingslashit( $wp_rewrite->comments_pagination_base . '-' . get_query_var('cpage'), 'commentpaged' );
				$redirect['query'] = remove_query_arg( 'cpage', $redirect['query'] );
			}

			$redirect['path'] = user_trailingslashit( preg_replace('|/' . preg_quote( $wp_rewrite->index, '|' ) . '/?$|', '/', $redirect['path']) ); // strip off trailing /index.php/
			if ( !empty( $addl_path ) && $wp_rewrite->using_index_permalinks() && strpos($redirect['path'], '/' . $wp_rewrite->index . '/') === false )
				$redirect['path'] = trailingslashit($redirect['path']) . $wp_rewrite->index . '/';
			if ( !empty( $addl_path ) )
				$redirect['path'] = trailingslashit($redirect['path']) . $addl_path;
			$redirect_url = $redirect['scheme'] . '://' . $redirect['host'] . $redirect['path'];
		}

		if ( 'wp-register.php' == basename( $redirect['path'] ) ) {
			if ( is_multisite() ) {
				/** This filter is documented in wp-login.php */
				$redirect_url = apply_filters( 'wp_signup_location', network_site_url( 'wp-signup.php' ) );
			} else {
				$redirect_url = wp_registration_url();
			}

			wp_redirect( $redirect_url, 301 );
			die();
		}
	}

	// tack on any additional query vars
	$redirect['query'] = preg_replace( '#^\??&*?#', '', $redirect['query'] );
	if ( $redirect_url && !empty($redirect['query']) ) {
		parse_str( $redirect['query'], $_parsed_query );
		$redirect = @parse_url($redirect_url);

		if ( ! empty( $_parsed_query['name'] ) && ! empty( $redirect['query'] ) ) {
			parse_str( $redirect['query'], $_parsed_redirect_query );

			if ( empty( $_parsed_redirect_query['name'] ) )
				unset( $_parsed_query['name'] );
		}

		$_parsed_query = rawurlencode_deep( $_parsed_query );
		$redirect_url = add_query_arg( $_parsed_query, $redirect_url );
	}

	if ( $redirect_url )
		$redirect = @parse_url($redirect_url);

	// www.example.com vs example.com
	$user_home = @parse_url(home_url());
	if ( !empty($user_home['host']) )
		$redirect['host'] = $user_home['host'];
	if ( empty($user_home['path']) )
		$user_home['path'] = '/';

	// Handle ports
	if ( !empty($user_home['port']) )
		$redirect['port'] = $user_home['port'];
	else
		unset($redirect['port']);

	// trailing /index.php
	$redirect['path'] = preg_replace('|/' . preg_quote( $wp_rewrite->index, '|' ) . '/*?$|', '/', $redirect['path']);

	$punctuation_pattern = implode( '|', array_map( 'preg_quote', array(
		' ', '%20',       // space
		'!', '%21',       // exclamation mark
		'"', '%22',       // double quote
		"'", '%27',       // single quote
		'(', '%28',       // opening bracket
		')', '%29',       // closing bracket
		',', '%2C',       // comma
		'.', '%2E',       // period
		';', '%3B',       // semicolon
		'{', '%7B',       // opening curly bracket
		'}', '%7D',       // closing curly bracket
		'“', '%E2%80%9C', // opening curly quote
		'”', '%E2%80%9D', // closing curly quote
	) ) );

	// Remove trailing spaces and end punctuation from the path.
	$redirect['path'] = preg_replace( "#($punctuation_pattern)+$#", '', $redirect['path'] );

	if ( !empty( $redirect['query'] ) ) {
		// Remove trailing spaces and end punctuation from certain terminating query string args.
		$redirect['query'] = preg_replace( "#((p|page_id|cat|tag)=[^&]*?)($punctuation_pattern)+$#", '$1', $redirect['query'] );

		// Clean up empty query strings
		$redirect['query'] = trim(preg_replace( '#(^|&)(p|page_id|cat|tag)=?(&|$)#', '&', $redirect['query']), '&');

		// Redirect obsolete feeds
		$redirect['query'] = preg_replace( '#(^|&)feed=rss(&|$)#', '$1feed=rss2$2', $redirect['query'] );

		// Remove redundant leading ampersands
		$redirect['query'] = preg_replace( '#^\??&*?#', '', $redirect['query'] );
	}

	// strip /index.php/ when we're not using PATHINFO permalinks
	if ( !$wp_rewrite->using_index_permalinks() )
		$redirect['path'] = str_replace( '/' . $wp_rewrite->index . '/', '/', $redirect['path'] );

	// trailing slashes
	if ( is_object($wp_rewrite) && $wp_rewrite->using_permalinks() && !is_404() && (!is_front_page() || ( is_front_page() && (get_query_var('paged') > 1) ) ) ) {
		$user_ts_type = '';
		if ( get_query_var('paged') > 0 ) {
			$user_ts_type = 'paged';
		} else {
			foreach ( array('single', 'category', 'page', 'day', 'month', 'year', 'home') as $type ) {
				$func = 'is_' . $type;
				if ( call_user_func($func) ) {
					$user_ts_type = $type;
					break;
				}
			}
		}
		$redirect['path'] = user_trailingslashit($redirect['path'], $user_ts_type);
	} elseif ( is_front_page() ) {
		$redirect['path'] = trailingslashit($redirect['path']);
	}

	// Strip multiple slashes out of the URL
	if ( strpos($redirect['path'], '//') > -1 )
		$redirect['path'] = preg_replace('|/+|', '/', $redirect['path']);

	// Always trailing slash the Front Page URL
	if ( trailingslashit( $redirect['path'] ) == trailingslashit( $user_home['path'] ) )
		$redirect['path'] = trailingslashit($redirect['path']);

	// Ignore differences in host capitalization, as this can lead to infinite redirects
	// Only redirect no-www <=> yes-www
	if ( strtolower($original['host']) == strtolower($redirect['host']) ||
		( strtolower($original['host']) != 'www.' . strtolower($redirect['host']) && 'www.' . strtolower($original['host']) != strtolower($redirect['host']) ) )
		$redirect['host'] = $original['host'];

	$compare_original = array( $original['host'], $original['path'] );

	if ( !empty( $original['port'] ) )
		$compare_original[] = $original['port'];

	if ( !empty( $original['query'] ) )
		$compare_original[] = $original['query'];

	$compare_redirect = array( $redirect['host'], $redirect['path'] );

	if ( !empty( $redirect['port'] ) )
		$compare_redirect[] = $redirect['port'];

	if ( !empty( $redirect['query'] ) )
		$compare_redirect[] = $redirect['query'];

	if ( $compare_original !== $compare_redirect ) {
		$redirect_url = $redirect['scheme'] . '://' . $redirect['host'];
		if ( !empty($redirect['port']) )
			$redirect_url .= ':' . $redirect['port'];
		$redirect_url .= $redirect['path'];
		if ( !empty($redirect['query']) )
			$redirect_url .= '?' . $redirect['query'];
	}

	if ( ! $redirect_url || $redirect_url == $requested_url ) {
		return;
	}

	// Hex encoded octets are case-insensitive.
	if ( false !== strpos($requested_url, '%') ) {
		if ( !function_exists('lowercase_octets') ) {
			/**
			 * Converts the first hex-encoded octet match to lowercase.
			 *
			 * @since 3.1.0
			 * @ignore
			 *
			 * @param array $matches Hex-encoded octet matches for the requested URL.
			 * @return string Lowercased version of the first match.
			 */
			function lowercase_octets($matches) {
				return strtolower( $matches[0] );
			}
		}
		$requested_url = preg_replace_callback('|%[a-fA-F0-9][a-fA-F0-9]|', 'lowercase_octets', $requested_url);
	}

	/**
	 * Filters the canonical redirect URL.
	 *
	 * Returning false to this filter will cancel the redirect.
	 *
	 * @since 2.3.0
	 *
	 * @param string $redirect_url  The redirect URL.
	 * @param string $requested_url The requested URL.
	 */
	$redirect_url = apply_filters( 'redirect_canonical', $redirect_url, $requested_url );

	// yes, again -- in case the filter aborted the request
	if ( ! $redirect_url || strip_fragment_from_url( $redirect_url ) == strip_fragment_from_url( $requested_url ) ) {
		return;
	}

	if ( $do_redirect ) {
		// protect against chained redirects
		if ( !redirect_canonical($redirect_url, false) ) {
			wp_redirect($redirect_url, 301);
			exit();
		} else {
			// Debug
			// die("1: $redirect_url<br />2: " . redirect_canonical( $redirect_url, false ) );
			return;
		}
	} else {
		return $redirect_url;
	}
}