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<?php
/**
* Canonical API to handle WordPress Redirecting
*
* Based on "Permalink Redirect" from Scott Yang and "Enforce www. Preference"
* by Mark Jaquith
*
* @author Scott Yang
* @author Mark Jaquith
* @package WordPress
* @since 2.3
*/
/**
* 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 penality for duplicate content by redirecting all incoming links to
* one or the other.
*
* Prevents redirection for feeds, trackbacks, searches, comment popup, and
* admin URLs. Does not redirect on IIS, page/post previews, and on form data.
*
* 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.
*
* @since 2.3
* @uses $wp_rewrite
* @uses $is_IIS
*
* @param string $requested_url Optional. The URL that was requested, used to
* figure if redirect is needed.
* @param bool $do_redirect Optional. Redirect to the new URL.
* @return null|false|string Null, if redirect not needed. False, if redirect
* not needed or the string of the URL
*/
function redirect_canonical($requested_url=null, $do_redirect=true) {
global $wp_rewrite, $is_IIS;
if ( is_feed() || is_trackback() || is_search() || is_comments_popup() || is_admin() || $is_IIS || ( isset($_POST) && count($_POST) ) || is_preview() || is_robots() )
return;
if ( !$requested_url ) {
// build the URL in the address bar
$requested_url = ( isset($_SERVER['HTTPS'] ) && strtolower($_SERVER['HTTPS']) == 'on' ) ? 'https://' : 'http://';
$requested_url .= $_SERVER['HTTP_HOST'];
$requested_url .= $_SERVER['REQUEST_URI'];
}
$original = @parse_url($requested_url);
if ( false === $original )
return;
// Some PHP setups turn requests for / into /index.php in REQUEST_URI
$original['path'] = preg_replace('|/index\.php$|', '/', $original['path']);
$redirect = $original;
$redirect_url = false;
// These tests give us a WP-generated permalink
if ( is_404() ) {
$redirect_url = redirect_guess_404_permalink();
} elseif ( is_object($wp_rewrite) && $wp_rewrite->using_permalinks() ) {
// rewriting of old ?p=X, ?m=2004, ?m=200401, ?m=20040101
if ( is_single() && isset($_GET['p']) ) {
if ( $redirect_url = get_permalink(get_query_var('p')) )
$redirect['query'] = remove_query_arg('p', $redirect['query']);
} elseif ( is_page() && isset($_GET['page_id']) ) {
if ( $redirect_url = get_permalink(get_query_var('page_id')) )
$redirect['query'] = remove_query_arg('page_id', $redirect['query']);
} elseif ( isset($_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', $redirect['query']);
// now moving on to non ?m=X year/month/day links
} elseif ( is_day() && get_query_var('year') && get_query_var('monthnum') && isset($_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'), $redirect['query']);
} elseif ( is_month() && get_query_var('year') && isset($_GET['monthnum']) ) {
if ( $redirect_url = get_month_link(get_query_var('year'), get_query_var('monthnum')) )
$redirect['query'] = remove_query_arg(array('year', 'monthnum'), $redirect['query']);
} elseif ( is_year() && isset($_GET['year']) ) {
if ( $redirect_url = get_year_link(get_query_var('year')) )
$redirect['query'] = remove_query_arg('year', $redirect['query']);
} elseif ( is_category() && isset($_GET['cat']) ) {
if ( $redirect_url = get_category_link(get_query_var('cat')) )
$redirect['query'] = remove_query_arg('cat', $redirect['query']);
} elseif ( is_author() && isset($_GET['author']) ) {
$author = get_userdata(get_query_var('author'));
if ( false !== $author && $redirect_url = get_author_link(false, $author->ID, $author->user_nicename) )
$redirect['query'] = remove_query_arg('author', $redirect['author']);
}
// paging
if ( $paged = get_query_var('paged') ) {
if ( $paged > 0 ) {
if ( !$redirect_url )
$redirect_url = $requested_url;
$paged_redirect = @parse_url($redirect_url);
$paged_redirect['path'] = preg_replace('|/page/[0-9]+?(/+)?$|', '/', $paged_redirect['path']); // strip off any existing paging
$paged_redirect['path'] = preg_replace('|/index.php/?$|', '/', $paged_redirect['path']); // strip off trailing /index.php/
if ( $paged > 1 && !is_single() ) {
$paged_redirect['path'] = trailingslashit($paged_redirect['path']);
if ( $wp_rewrite->using_index_permalinks() && strpos($paged_redirect['path'], '/index.php/') === false )
$paged_redirect['path'] .= 'index.php/';
$paged_redirect['path'] .= user_trailingslashit("page/$paged", 'paged');
} elseif ( !is_home() && !is_single() ){
$paged_redirect['path'] = user_trailingslashit($paged_redirect['path'], 'paged');
}
$redirect_url = $paged_redirect['scheme'] . '://' . $paged_redirect['host'] . $paged_redirect['path'];
$redirect['path'] = $paged_redirect['path'];
}
$redirect['query'] = remove_query_arg('paged', $redirect['query']);
}
}
// tack on any additional query vars
if ( $redirect_url && $redirect['query'] ) {
if ( strpos($redirect_url, '?') !== false )
$redirect_url .= '&';
else
$redirect_url .= '?';
$redirect_url .= $redirect['query'];
}
if ( $redirect_url )
$redirect = @parse_url($redirect_url);
// www.example.com vs example.com
$user_home = @parse_url(get_option('home'));
if ( isset($user_home['host']) )
$redirect['host'] = $user_home['host'];
// Handle ports
if ( isset($user_home['port']) )
$redirect['port'] = $user_home['port'];
else
unset($redirect['port']);
// trailing /index.php/
$redirect['path'] = preg_replace('|/index.php/$|', '/', $redirect['path']);
// strip /index.php/ when we're not using PATHINFO permalinks
if ( !$wp_rewrite->using_index_permalinks() )
$redirect['path'] = str_replace('/index.php/', '/', $redirect['path']);
// trailing slashes
if ( is_object($wp_rewrite) && $wp_rewrite->using_permalinks() && !is_404() && (!is_home() || ( is_home() && (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') 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_home() ) {
$redirect['path'] = trailingslashit($redirect['path']);
}
// Always trailing slash the 'home' URL
if ( $redirect['path'] == $user_home['path'] )
$redirect['path'] = trailingslashit($redirect['path']);
// Ignore differences in host capitalization, as this can lead to infinite redirects
if ( strtolower($original['host']) == strtolower($redirect['host']) )
$redirect['host'] = $original['host'];
if ( array($original['host'], $original['port'], $original['path'], $original['query']) !== array($redirect['host'], $redirect['port'], $redirect['path'], $redirect['query']) ) {
$redirect_url = $redirect['scheme'] . '://' . $redirect['host'];
if ( isset($redirect['port']) )
$redirect_url .= ':' . $redirect['port'];
$redirect_url .= $redirect['path'];
if ( $redirect['query'] )
$redirect_url .= '?' . $redirect['query'];
}
if ( !$redirect_url || $redirect_url == $requested_url )
return false;
// Note that you can use the "redirect_canonical" filter to cancel a canonical redirect for whatever reason by returning FALSE
$redirect_url = apply_filters('redirect_canonical', $redirect_url, $requested_url);
if ( !$redirect_url || $redirect_url == $requested_url ) // yes, again -- in case the filter aborted the request
return false;
if ( $do_redirect ) {
// protect against chained redirects
if ( !redirect_canonical($redirect_url, false) ) {
wp_redirect($redirect_url, 301);
exit();
} else {
return false;
}
} else {
return $redirect_url;
}
}
/**
* Attempts to guess correct post based on query vars
*
* @since 2.3
* @uses $wpdb
*
* @return bool|string Returns False, if it can't find post, returns correct
* location on success.
*/
function redirect_guess_404_permalink() {
global $wpdb;
if ( !get_query_var('name') )
return false;
$where = $wpdb->prepare("post_name LIKE %s", get_query_var('name') . '%');
// if any of year, monthnum, or day are set, use them to refine the query
if ( get_query_var('year') )
$where .= $wpdb->prepare(" AND YEAR(post_date) = %d", get_query_var('year'));
if ( get_query_var('monthnum') )
$where .= $wpdb->prepare(" AND MONTH(post_date) = %d", get_query_var('monthnum'));
if ( get_query_var('day') )
$where .= $wpdb->prepare(" AND DAYOFMONTH(post_date) = %d", get_query_var('day'));
$post_id = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE $where AND post_status = 'publish'");
if ( !$post_id )
return false;
return get_permalink($post_id);
}
add_action('template_redirect', 'redirect_canonical');
?>
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