WordPress/wp-includes/rewrite-functions.php

<?php
/**
 * WordPress Rewrite API
 *
 * @package WordPress
 * @subpackage Rewrite
 */

/**
 * Add a straight rewrite rule.
 *
 * @since 2.1.0
 *
 * @global WP_Rewrite $wp_rewrite
 *
 * @param string $regex    Regular Expression to match request against.
 * @param string $redirect Page to redirect to.
 * @param string $after    Optional, default is 'bottom'. Where to add rule, can also be 'top'.
 */
function add_rewrite_rule($regex, $redirect, $after = 'bottom') {
	global $wp_rewrite;
	$wp_rewrite->add_rule($regex, $redirect, $after);
}

/**
 * Add a new rewrite tag (like %postname%).
 *
 * The $query parameter is optional. If it is omitted you must ensure that
 * you call this on, or before, the 'init' hook. This is because $query defaults
 * to "$tag=", and for this to work a new query var has to be added.
 *
 * @since 2.1.0
 *
 * @global WP_Rewrite $wp_rewrite
 * @global WP         $wp
 *
 * @param string $tag   Name of the new rewrite tag.
 * @param string $regex Regular expression to substitute the tag for in rewrite rules.
 * @param string $query String to append to the rewritten query. Must end in '='. Optional.
 */
function add_rewrite_tag( $tag, $regex, $query = '' ) {
	// validate the tag's name
	if ( strlen( $tag ) < 3 || $tag[0] != '%' || $tag[ strlen($tag) - 1 ] != '%' )
		return;

	global $wp_rewrite, $wp;

	if ( empty( $query ) ) {
		$qv = trim( $tag, '%' );
		$wp->add_query_var( $qv );
		$query = $qv . '=';
	}

	$wp_rewrite->add_rewrite_tag( $tag, $regex, $query );
}

/**
 * Add permalink structure.
 *
 * @since 3.0.0
 *
 * @global WP_Rewrite $wp_rewrite
 *
 * @param string $name   Name for permalink structure.
 * @param string $struct Permalink structure.
 * @param array  $args   Optional configuration for building the rules from the permalink structure,
 *                       see {@link WP_Rewrite::add_permastruct()} for full details.
 */
function add_permastruct( $name, $struct, $args = array() ) {
	global $wp_rewrite;

	// backwards compatibility for the old parameters: $with_front and $ep_mask
	if ( ! is_array( $args ) )
		$args = array( 'with_front' => $args );
	if ( func_num_args() == 4 )
		$args['ep_mask'] = func_get_arg( 3 );

	$wp_rewrite->add_permastruct( $name, $struct, $args );
}

/**
 * Add a new feed type like /atom1/.
 *
 * @since 2.1.0
 *
 * @global WP_Rewrite $wp_rewrite
 *
 * @param string   $feedname
 * @param callback $function Callback to run on feed display.
 * @return string Feed action name.
 */
function add_feed($feedname, $function) {
	global $wp_rewrite;
	if ( ! in_array($feedname, $wp_rewrite->feeds) ) //override the file if it is
		$wp_rewrite->feeds[] = $feedname;
	$hook = 'do_feed_' . $feedname;
	// Remove default function hook
	remove_action($hook, $hook);
	add_action($hook, $function, 10, 1);
	return $hook;
}

/**
 * Remove rewrite rules and then recreate rewrite rules.
 *
 * @since 3.0.0
 *
 * @global WP_Rewrite $wp_rewrite
 *
 * @param bool $hard Whether to update .htaccess (hard flush) or just update
 * 	                 rewrite_rules transient (soft flush). Default is true (hard).
 */
function flush_rewrite_rules( $hard = true ) {
	global $wp_rewrite;
	$wp_rewrite->flush_rules( $hard );
}

/**
 * Add an endpoint, like /trackback/.
 *
 * Adding an endpoint creates extra rewrite rules for each of the matching
 * places specified by the provided bitmask. For example:
 *
 *     add_rewrite_endpoint( 'json', EP_PERMALINK | EP_PAGES );
 *
 * will add a new rewrite rule ending with "json(/(.*))?/?$" for every permastruct
 * that describes a permalink (post) or page. This is rewritten to "json=$match"
 * where $match is the part of the URL matched by the endpoint regex (e.g. "foo" in
 * "[permalink]/json/foo/").
 *
 * A new query var with the same name as the endpoint will also be created.
 *
 * When specifying $places ensure that you are using the EP_* constants (or a
 * combination of them using the bitwise OR operator) as their values are not
 * guaranteed to remain static (especially `EP_ALL`).
 *
 * Be sure to flush the rewrite rules - see flush_rewrite_rules() - when your plugin gets
 * activated and deactivated.
 *
 * @since 2.1.0
 * @since 4.3.0 Added support for skipping query var registration by passing `false` to `$query_var`.
 *
 * @global WP_Rewrite $wp_rewrite
 *
 * @param string      $name      Name of the endpoint.
 * @param int         $places    Endpoint mask describing the places the endpoint should be added.
 * @param string|bool $query_var Name of the corresponding query variable. Pass `false` to skip registering a query_var
 *                               for this endpoint. Defaults to the value of `$name`.
 */
function add_rewrite_endpoint( $name, $places, $query_var = true ) {
	global $wp_rewrite;
	$wp_rewrite->add_endpoint( $name, $places, $query_var );
}

/**
 * Filter the URL base for taxonomies.
 *
 * To remove any manually prepended /index.php/.
 *
 * @access private
 * @since 2.6.0
 *
 * @param string $base The taxonomy base that we're going to filter
 * @return string
 */
function _wp_filter_taxonomy_base( $base ) {
	if ( !empty( $base ) ) {
		$base = preg_replace( '|^/index\.php/|', '', $base );
		$base = trim( $base, '/' );
	}
	return $base;
}


/**
 * Resolve numeric slugs that collide with date permalinks.
 *
 * Permalinks of posts with numeric slugs can sometimes look to WP_Query::parse_query()
 * like a date archive, as when your permalink structure is `/%year%/%postname%/` and
 * a post with post_name '05' has the URL `/2015/05/`.
 *
 * This function detects conflicts of this type and resolves them in favor of the
 * post permalink.
 *
 * Note that, since 4.3.0, wp_unique_post_slug() prevents the creation of post slugs
 * that would result in a date archive conflict. The resolution performed in this
 * function is primarily for legacy content, as well as cases when the admin has changed
 * the site's permalink structure in a way that introduces URL conflicts.
 *
 * @since 4.3.0
 *
 * @param array $query_vars Optional. Query variables for setting up the loop, as determined in
 *                          WP::parse_request(). Default empty array.
 * @return array Returns the original array of query vars, with date/post conflicts resolved.
 */
function wp_resolve_numeric_slug_conflicts( $query_vars = array() ) {
	if ( ! isset( $query_vars['year'] ) && ! isset( $query_vars['monthnum'] ) && ! isset( $query_vars['day'] ) ) {
		return $query_vars;
	}

	// Identify the 'postname' position in the permastruct array.
	$permastructs   = array_values( array_filter( explode( '/', get_option( 'permalink_structure' ) ) ) );
	$postname_index = array_search( '%postname%', $permastructs );

	if ( false === $postname_index ) {
		return $query_vars;
	}

	/*
	 * A numeric slug could be confused with a year, month, or day, depending on position. To account for
	 * the possibility of post pagination (eg 2015/2 for the second page of a post called '2015'), our
	 * `is_*` checks are generous: check for year-slug clashes when `is_year` *or* `is_month`, and check
	 * for month-slug clashes when `is_month` *or* `is_day`.
	 */
	$compare = '';
	if ( 0 === $postname_index && ( isset( $query_vars['year'] ) || isset( $query_vars['monthnum'] ) ) ) {
		$compare = 'year';
	} elseif ( '%year%' === $permastructs[ $postname_index - 1 ] && ( isset( $query_vars['monthnum'] ) || isset( $query_vars['day'] ) ) ) {
		$compare = 'monthnum';
	} elseif ( '%monthnum%' === $permastructs[ $postname_index - 1 ] && isset( $query_vars['day'] ) ) {
		$compare = 'day';
	}

	if ( ! $compare ) {
		return $query_vars;
	}

	// This is the potentially clashing slug.
	$value = $query_vars[ $compare ];

	$post = get_page_by_path( $value, OBJECT, 'post' );
	if ( ! ( $post instanceof WP_Post ) ) {
		return $query_vars;
	}

	// If the date of the post doesn't match the date specified in the URL, resolve to the date archive.
	if ( preg_match( '/^([0-9]{4})\-([0-9]{2})/', $post->post_date, $matches ) && isset( $query_vars['year'] ) && ( 'monthnum' === $compare || 'day' === $compare ) ) {
		// $matches[1] is the year the post was published.
		if ( intval( $query_vars['year'] ) !== intval( $matches[1] ) ) {
			return $query_vars;
		}

		// $matches[2] is the month the post was published.
		if ( 'day' === $compare && isset( $query_vars['monthnum'] ) && intval( $query_vars['monthnum'] ) !== intval( $matches[2] ) ) {
			return $query_vars;
		}
	}

	/*
	 * If the located post contains nextpage pagination, then the URL chunk following postname may be
	 * intended as the page number. Verify that it's a valid page before resolving to it.
	 */
	$maybe_page = '';
	if ( 'year' === $compare && isset( $query_vars['monthnum'] ) ) {
		$maybe_page = $query_vars['monthnum'];
	} elseif ( 'monthnum' === $compare && isset( $query_vars['day'] ) ) {
		$maybe_page = $query_vars['day'];
	}
	// Bug found in #11694 - 'page' was returning '/4'
	$maybe_page = (int) trim( $maybe_page, '/' );

	$post_page_count = substr_count( $post->post_content, '<!--nextpage-->' ) + 1;

	// If the post doesn't have multiple pages, but a 'page' candidate is found, resolve to the date archive.
	if ( 1 === $post_page_count && $maybe_page ) {
		return $query_vars;
	}

	// If the post has multiple pages and the 'page' number isn't valid, resolve to the date archive.
	if ( $post_page_count > 1 && $maybe_page > $post_page_count ) {
		return $query_vars;
	}

	// If we've gotten to this point, we have a slug/date clash. First, adjust for nextpage.
	if ( '' !== $maybe_page ) {
		$query_vars['page'] = intval( $maybe_page );
	}

	// Next, unset autodetected date-related query vars.
	unset( $query_vars['year'] );
	unset( $query_vars['monthnum'] );
	unset( $query_vars['day'] );

	// Then, set the identified post.
	$query_vars['name'] = $post->post_name;

	// Finally, return the modified query vars.
	return $query_vars;
}

/**
 * Examine a url and try to determine the post ID it represents.
 *
 * Checks are supposedly from the hosted site blog.
 *
 * @since 1.0.0
 *
 * @global WP_Rewrite $wp_rewrite
 * @global WP         $wp
 *
 * @param string $url Permalink to check.
 * @return int Post ID, or 0 on failure.
 */
function url_to_postid( $url ) {
	global $wp_rewrite;

	/**
	 * Filter the URL to derive the post ID from.
	 *
	 * @since 2.2.0
	 *
	 * @param string $url The URL to derive the post ID from.
	 */
	$url = apply_filters( 'url_to_postid', $url );

	// First, check to see if there is a 'p=N' or 'page_id=N' to match against
	if ( preg_match('#[?&](p|page_id|attachment_id)=(\d+)#', $url, $values) )	{
		$id = absint($values[2]);
		if ( $id )
			return $id;
	}

	// Check to see if we are using rewrite rules
	$rewrite = $wp_rewrite->wp_rewrite_rules();

	// Not using rewrite rules, and 'p=N' and 'page_id=N' methods failed, so we're out of options
	if ( empty($rewrite) )
		return 0;

	// Get rid of the #anchor
	$url_split = explode('#', $url);
	$url = $url_split[0];

	// Get rid of URL ?query=string
	$url_split = explode('?', $url);
	$url = $url_split[0];

	// Add 'www.' if it is absent and should be there
	if ( false !== strpos(home_url(), '://www.') && false === strpos($url, '://www.') )
		$url = str_replace('://', '://www.', $url);

	// Strip 'www.' if it is present and shouldn't be
	if ( false === strpos(home_url(), '://www.') )
		$url = str_replace('://www.', '://', $url);

	// Strip 'index.php/' if we're not using path info permalinks
	if ( !$wp_rewrite->using_index_permalinks() )
		$url = str_replace( $wp_rewrite->index . '/', '', $url );

	if ( false !== strpos( trailingslashit( $url ), home_url( '/' ) ) ) {
		// Chop off http://domain.com/[path]
		$url = str_replace(home_url(), '', $url);
	} else {
		// Chop off /path/to/blog
		$home_path = parse_url( home_url( '/' ) );
		$home_path = isset( $home_path['path'] ) ? $home_path['path'] : '' ;
		$url = preg_replace( sprintf( '#^%s#', preg_quote( $home_path ) ), '', trailingslashit( $url ) );
	}

	// Trim leading and lagging slashes
	$url = trim($url, '/');

	$request = $url;
	$post_type_query_vars = array();

	foreach ( get_post_types( array() , 'objects' ) as $post_type => $t ) {
		if ( ! empty( $t->query_var ) )
			$post_type_query_vars[ $t->query_var ] = $post_type;
	}

	// Look for matches.
	$request_match = $request;
	foreach ( (array)$rewrite as $match => $query) {

		// If the requesting file is the anchor of the match, prepend it
		// to the path info.
		if ( !empty($url) && ($url != $request) && (strpos($match, $url) === 0) )
			$request_match = $url . '/' . $request;

		if ( preg_match("#^$match#", $request_match, $matches) ) {

			if ( $wp_rewrite->use_verbose_page_rules && preg_match( '/pagename=\$matches\[([0-9]+)\]/', $query, $varmatch ) ) {
				// This is a verbose page match, let's check to be sure about it.
				if ( ! get_page_by_path( $matches[ $varmatch[1] ] ) )
					continue;
			}

			// Got a match.
			// Trim the query of everything up to the '?'.
			$query = preg_replace("!^.+\?!", '', $query);

			// Substitute the substring matches into the query.
			$query = addslashes(WP_MatchesMapRegex::apply($query, $matches));

			// Filter out non-public query vars
			global $wp;
			parse_str( $query, $query_vars );
			$query = array();
			foreach ( (array) $query_vars as $key => $value ) {
				if ( in_array( $key, $wp->public_query_vars ) ){
					$query[$key] = $value;
					if ( isset( $post_type_query_vars[$key] ) ) {
						$query['post_type'] = $post_type_query_vars[$key];
						$query['name'] = $value;
					}
				}
			}

			// Resolve conflicts between posts with numeric slugs and date archive queries.
			$query = wp_resolve_numeric_slug_conflicts( $query );

			// Do the query
			$query = new WP_Query( $query );
			if ( ! empty( $query->posts ) && $query->is_singular )
				return $query->post->ID;
			else
				return 0;
		}
	}
	return 0;
}