wp/wp-includes/link-template.php
changeset 5 5e2f62d02dcd
parent 0 d970ebf37754
child 7 cf61fcea0001
--- a/wp/wp-includes/link-template.php	Mon Jun 08 16:11:51 2015 +0000
+++ b/wp/wp-includes/link-template.php	Tue Jun 09 03:35:32 2015 +0200
@@ -10,9 +10,15 @@
  * Display the permalink for the current post.
  *
  * @since 1.2.0
- * @uses apply_filters() Calls 'the_permalink' filter on the permalink string.
  */
 function the_permalink() {
+	/**
+	 * Filter the display of the permalink for the current post.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $permalink The permalink for the current post.
+	 */
 	echo esc_url( apply_filters( 'the_permalink', get_permalink() ) );
 }
 
@@ -29,7 +35,7 @@
  *
  * @param string $string URL with or without a trailing slash.
  * @param string $type_of_url The type of URL being considered (e.g. single, category, etc) for use in the filter.
- * @return string
+ * @return string The URL with the trailing slash appended or stripped.
  */
 function user_trailingslashit($string, $type_of_url = '') {
 	global $wp_rewrite;
@@ -38,9 +44,18 @@
 	else
 		$string = untrailingslashit($string);
 
-	// Note that $type_of_url can be one of following:
-	// single, single_trackback, single_feed, single_paged, feed, category, page, year, month, day, paged, post_type_archive
-	$string = apply_filters('user_trailingslashit', $string, $type_of_url);
+	/**
+	 * Filter the trailing slashed string, depending on whether the site is set
+	 * to use training slashes.
+	 *
+	 * @since 2.2.0
+	 *
+	 * @param string $string      URL with or without a trailing slash.
+	 * @param string $type_of_url The type of URL being considered. Accepts 'single', 'single_trackback',
+	 *                            'single_feed', 'single_paged', 'feed', 'category', 'page', 'year',
+	 *                            'month', 'day', 'paged', 'post_type_archive'.
+	 */
+	$string = apply_filters( 'user_trailingslashit', $string, $type_of_url );
 	return $string;
 }
 
@@ -71,10 +86,27 @@
 /**
  * Retrieve full permalink for current post or post ID.
  *
+ * This function is an alias for get_permalink().
+ *
+ * @since 3.9.0
+ *
+ * @see get_permalink()
+ *
+ * @param int|WP_Post $id        Optional. Post ID or post object. Default is the current post.
+ * @param bool        $leavename Optional. Whether to keep post name or page name. Default false.
+ * @return string|bool The permalink URL or false if post does not exist.
+ */
+function get_the_permalink( $id = 0, $leavename = false ) {
+	return get_permalink( $id, $leavename );
+}
+
+/**
+ * Retrieve full permalink for current post or post ID.
+ *
  * @since 1.0.0
  *
- * @param int|WP_Post $id Optional. Post ID or post object, defaults to the current post.
- * @param bool $leavename Optional. Whether to keep post name or page name, defaults to false.
+ * @param int|WP_Post $id        Optional. Post ID or post object. Default current post.
+ * @param bool        $leavename Optional. Whether to keep post name or page name. Default false.
  * @return string|bool The permalink URL or false if post does not exist.
  */
 function get_permalink( $id = 0, $leavename = false ) {
@@ -104,17 +136,28 @@
 		return false;
 
 	if ( $post->post_type == 'page' )
-		return get_page_link($post->ID, $leavename, $sample);
+		return get_page_link($post, $leavename, $sample);
 	elseif ( $post->post_type == 'attachment' )
-		return get_attachment_link( $post->ID, $leavename );
+		return get_attachment_link( $post, $leavename );
 	elseif ( in_array($post->post_type, get_post_types( array('_builtin' => false) ) ) )
-		return get_post_permalink($post->ID, $leavename, $sample);
+		return get_post_permalink($post, $leavename, $sample);
 
 	$permalink = get_option('permalink_structure');
 
-	$permalink = apply_filters('pre_post_link', $permalink, $post, $leavename);
-
-	if ( '' != $permalink && !in_array($post->post_status, array('draft', 'pending', 'auto-draft')) ) {
+	/**
+	 * Filter the permalink structure for a post before token replacement occurs.
+	 *
+	 * Only applies to posts with post_type of 'post'.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param string  $permalink The site's permalink structure.
+	 * @param WP_Post $post      The post in question.
+	 * @param bool    $leavename Whether to keep the post name.
+	 */
+	$permalink = apply_filters( 'pre_post_link', $permalink, $post, $leavename );
+
+	if ( '' != $permalink && !in_array( $post->post_status, array( 'draft', 'pending', 'auto-draft', 'future' ) ) ) {
 		$unixtime = strtotime($post->post_date);
 
 		$category = '';
@@ -122,7 +165,18 @@
 			$cats = get_the_category($post->ID);
 			if ( $cats ) {
 				usort($cats, '_usort_terms_by_ID'); // order by ID
+
+				/**
+				 * Filter the category that gets used in the %category% permalink token.
+				 *
+				 * @since 3.5.0
+				 *
+				 * @param stdClass $cat  The category to use in the permalink.
+				 * @param array    $cats Array of all categories associated with the post.
+				 * @param WP_Post  $post The post in question.
+				 */
 				$category_object = apply_filters( 'post_link_category', $cats[0], $cats, $post );
+
 				$category_object = get_term( $category_object, 'category' );
 				$category = $category_object->slug;
 				if ( $parent = $category_object->parent )
@@ -162,7 +216,19 @@
 	} else { // if they're not using the fancy permalink option
 		$permalink = home_url('?p=' . $post->ID);
 	}
-	return apply_filters('post_link', $permalink, $post, $leavename);
+
+	/**
+	 * Filter the permalink for a post.
+	 *
+	 * Only applies to posts with post_type of 'post'.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string  $permalink The post's permalink.
+	 * @param WP_Post $post      The post in question.
+	 * @param bool    $leavename Whether to keep the post name.
+	 */
+	return apply_filters( 'post_link', $permalink, $post, $leavename );
 }
 
 /**
@@ -173,7 +239,7 @@
  * @param int $id Optional. Post ID.
  * @param bool $leavename Optional, defaults to false. Whether to keep post name.
  * @param bool $sample Optional, defaults to false. Is it a sample permalink.
- * @return string
+ * @return string The post permalink.
  */
 function get_post_permalink( $id = 0, $leavename = false, $sample = false ) {
 	global $wp_rewrite;
@@ -187,14 +253,16 @@
 
 	$slug = $post->post_name;
 
-	$draft_or_pending = isset($post->post_status) && in_array( $post->post_status, array( 'draft', 'pending', 'auto-draft' ) );
+	$draft_or_pending = isset( $post->post_status ) && in_array( $post->post_status, array( 'draft', 'pending', 'auto-draft', 'future' ) );
 
 	$post_type = get_post_type_object($post->post_type);
 
+	if ( $post_type->hierarchical ) {
+		$slug = get_page_uri( $id );
+	}
+
 	if ( !empty($post_link) && ( !$draft_or_pending || $sample ) ) {
 		if ( ! $leavename ) {
-			if ( $post_type->hierarchical )
-				$slug = get_page_uri($id);
 			$post_link = str_replace("%$post->post_type%", $slug, $post_link);
 		}
 		$post_link = home_url( user_trailingslashit($post_link) );
@@ -206,7 +274,17 @@
 		$post_link = home_url($post_link);
 	}
 
-	return apply_filters('post_type_link', $post_link, $post, $leavename, $sample);
+	/**
+	 * Filter the permalink for a post with a custom post type.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param string  $post_link The post's permalink.
+	 * @param WP_Post $post      The post in question.
+	 * @param bool    $leavename Whether to keep the post name.
+	 * @param bool    $sample    Is it a sample permalink.
+	 */
+	return apply_filters( 'post_type_link', $post_link, $post, $leavename, $sample );
 }
 
 /**
@@ -214,7 +292,7 @@
  *
  * @since 1.0.0
  *
- * @param int $post_id Optional. Post ID.
+ * @param int|WP_Post $post_id Optional. Post ID or WP_Post object. Default is global $post.
  * @param mixed $deprecated Not used.
  * @return string
  */
@@ -235,7 +313,7 @@
  * @param int|object $post Optional. Post ID or object.
  * @param bool $leavename Optional, defaults to false. Whether to keep page name.
  * @param bool $sample Optional, defaults to false. Is it a sample permalink.
- * @return string
+ * @return string The page permalink.
  */
 function get_page_link( $post = false, $leavename = false, $sample = false ) {
 	$post = get_post( $post );
@@ -245,6 +323,15 @@
 	else
 		$link = _get_page_link( $post, $leavename, $sample );
 
+	/**
+	 * Filter the permalink for a page.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $link    The page's permalink.
+	 * @param int    $post_id The ID of the page.
+	 * @param bool   $sample  Is it a sample permalink.
+	 */
 	return apply_filters( 'page_link', $link, $post->ID, $sample );
 }
 
@@ -259,7 +346,7 @@
  * @param int|object $post Optional. Post ID or object.
  * @param bool $leavename Optional. Leave name.
  * @param bool $sample Optional. Sample permalink.
- * @return string
+ * @return string The page permalink.
  */
 function _get_page_link( $post = false, $leavename = false, $sample = false ) {
 	global $wp_rewrite;
@@ -281,6 +368,14 @@
 		$link = home_url( '?page_id=' . $post->ID );
 	}
 
+	/**
+	 * Filter the permalink for a non-page_on_front page.
+	 *
+	 * @since 2.1.0
+	 *
+	 * @param string $link    The page's permalink.
+	 * @param int    $post_id The ID of the page.
+	 */
 	return apply_filters( '_get_page_link', $link, $post->ID );
 }
 
@@ -293,7 +388,7 @@
  *
  * @param int|object $post Optional. Post ID or object.
  * @param bool $leavename Optional. Leave name.
- * @return string
+ * @return string The attachment permalink.
  */
 function get_attachment_link( $post = null, $leavename = false ) {
 	global $wp_rewrite;
@@ -324,6 +419,14 @@
 	if ( ! $link )
 		$link = home_url( '/?attachment_id=' . $post->ID );
 
+	/**
+	 * Filter the permalink for an attachment.
+	 *
+	 * @since 2.0.0
+	 *
+	 * @param string $link    The attachment's permalink.
+	 * @param int    $post_id Attachment ID.
+	 */
 	return apply_filters( 'attachment_link', $link, $post->ID );
 }
 
@@ -333,7 +436,7 @@
  * @since 1.5.0
  *
  * @param int|bool $year False for current year or year for permalink.
- * @return string
+ * @return string The permalink for the specified year archive.
  */
 function get_year_link($year) {
 	global $wp_rewrite;
@@ -342,10 +445,20 @@
 	$yearlink = $wp_rewrite->get_year_permastruct();
 	if ( !empty($yearlink) ) {
 		$yearlink = str_replace('%year%', $year, $yearlink);
-		return apply_filters('year_link', home_url( user_trailingslashit($yearlink, 'year') ), $year);
+		$yearlink = home_url( user_trailingslashit( $yearlink, 'year' ) );
 	} else {
-		return apply_filters('year_link', home_url('?m=' . $year), $year);
+		$yearlink = home_url( '?m=' . $year );
 	}
+
+	/**
+	 * Filter the year archive permalink.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $yearlink Permalink for the year archive.
+	 * @param int    $year     Year for the archive.
+	 */
+	return apply_filters( 'year_link', $yearlink, $year );
 }
 
 /**
@@ -355,7 +468,7 @@
  *
  * @param bool|int $year False for current year. Integer of year.
  * @param bool|int $month False for current month. Integer of month.
- * @return string
+ * @return string The permalink for the specified month and year archive.
  */
 function get_month_link($year, $month) {
 	global $wp_rewrite;
@@ -367,10 +480,21 @@
 	if ( !empty($monthlink) ) {
 		$monthlink = str_replace('%year%', $year, $monthlink);
 		$monthlink = str_replace('%monthnum%', zeroise(intval($month), 2), $monthlink);
-		return apply_filters('month_link', home_url( user_trailingslashit($monthlink, 'month') ), $year, $month);
+		$monthlink = home_url( user_trailingslashit( $monthlink, 'month' ) );
 	} else {
-		return apply_filters('month_link', home_url( '?m=' . $year . zeroise($month, 2) ), $year, $month);
+		$monthlink = home_url( '?m=' . $year . zeroise( $month, 2 ) );
 	}
+
+	/**
+	 * Filter the month archive permalink.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $monthlink Permalink for the month archive.
+	 * @param int    $year      Year for the archive.
+	 * @param int    $month     The month for the archive.
+	 */
+	return apply_filters( 'month_link', $monthlink, $year, $month );
 }
 
 /**
@@ -381,7 +505,7 @@
  * @param bool|int $year False for current year. Integer of year.
  * @param bool|int $month False for current month. Integer of month.
  * @param bool|int $day False for current day. Integer of day.
- * @return string
+ * @return string The permalink for the specified day, month, and year archive.
  */
 function get_day_link($year, $month, $day) {
 	global $wp_rewrite;
@@ -397,10 +521,22 @@
 		$daylink = str_replace('%year%', $year, $daylink);
 		$daylink = str_replace('%monthnum%', zeroise(intval($month), 2), $daylink);
 		$daylink = str_replace('%day%', zeroise(intval($day), 2), $daylink);
-		return apply_filters('day_link', home_url( user_trailingslashit($daylink, 'day') ), $year, $month, $day);
+		$daylink = home_url( user_trailingslashit( $daylink, 'day' ) );
 	} else {
-		return apply_filters('day_link', home_url( '?m=' . $year . zeroise($month, 2) . zeroise($day, 2) ), $year, $month, $day);
+		$daylink = home_url( '?m=' . $year . zeroise( $month, 2 ) . zeroise( $day, 2 ) );
 	}
+
+	/**
+	 * Filter the day archive permalink.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $daylink Permalink for the day archive.
+	 * @param int    $year    Year for the archive.
+	 * @param int    $month   Month for the archive.
+	 * @param int    $day     The day for the archive.
+	 */
+	return apply_filters( 'day_link', $daylink, $year, $month, $day );
 }
 
 /**
@@ -413,6 +549,16 @@
  */
 function the_feed_link( $anchor, $feed = '' ) {
 	$link = '<a href="' . esc_url( get_feed_link( $feed ) ) . '">' . $anchor . '</a>';
+
+	/**
+	 * Filter the feed link anchor tag.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param string $link The complete anchor tag for a feed link.
+	 * @param string $feed The feed type, or an empty string for the
+	 *                     default feed type.
+	 */
 	echo apply_filters( 'the_feed_link', $link, $feed );
 }
 
@@ -422,7 +568,7 @@
  * @since 1.5.0
  *
  * @param string $feed Optional, defaults to default feed. Feed type.
- * @return string
+ * @return string The feed permalink.
  */
 function get_feed_link($feed = '') {
 	global $wp_rewrite;
@@ -450,7 +596,15 @@
 		$output = home_url("?feed={$feed}");
 	}
 
-	return apply_filters('feed_link', $output, $feed);
+	/**
+	 * Filter the feed type permalink.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $output The feed permalink.
+	 * @param string $feed   Feed type.
+	 */
+	return apply_filters( 'feed_link', $output, $feed );
 }
 
 /**
@@ -460,7 +614,7 @@
  *
  * @param int $post_id Optional. Post ID.
  * @param string $feed Optional. Feed type.
- * @return string
+ * @return string The permalink for the comments feed for the given post.
  */
 function get_post_comments_feed_link($post_id = 0, $feed = '') {
 	$post_id = absint( $post_id );
@@ -489,7 +643,14 @@
 			$url = add_query_arg( array( 'feed' => $feed, 'p' => $post_id ), home_url( '/' ) );
 	}
 
-	return apply_filters('post_comments_feed_link', $url);
+	/**
+	 * Filter the post comments feed permalink.
+	 *
+	 * @since 1.5.1
+	 *
+	 * @param string $url Post comments feed permalink.
+	 */
+	return apply_filters( 'post_comments_feed_link', $url );
 }
 
 /**
@@ -499,8 +660,6 @@
  * anchor. If no link text is specified, default text is used. If no post ID is
  * specified, the current post is used.
  *
- * @package WordPress
- * @subpackage Feed
  * @since 2.5.0
  *
  * @param string $link_text Descriptive text.
@@ -513,6 +672,15 @@
 	if ( empty($link_text) )
 		$link_text = __('Comments Feed');
 
+	/**
+	 * Filter the post comment feed link anchor tag.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @param string $link    The complete anchor tag for the comment feed link.
+	 * @param int    $post_id Post ID.
+	 * @param string $feed    The feed type, or an empty string for the default feed type.
+	 */
 	echo apply_filters( 'post_comments_feed_link_html', "<a href='$url'>$link_text</a>", $post_id, $feed );
 }
 
@@ -522,8 +690,6 @@
  * Returns a link to the feed for all posts by a given author. A specific feed
  * can be requested or left blank to get the default feed.
  *
- * @package WordPress
- * @subpackage Feed
  * @since 2.5.0
  *
  * @param int $author_id ID of an author.
@@ -549,7 +715,15 @@
 		$link = trailingslashit($link) . user_trailingslashit($feed_link, 'feed');
 	}
 
-	$link = apply_filters('author_feed_link', $link, $feed);
+	/**
+	 * Filter the feed link for a given author.
+	 *
+	 * @since 1.5.1
+	 *
+	 * @param string $link The author feed link.
+	 * @param string $feed Feed type.
+	 */
+	$link = apply_filters( 'author_feed_link', $link, $feed );
 
 	return $link;
 }
@@ -560,8 +734,6 @@
  * Returns a link to the feed for all posts in a given category. A specific feed
  * can be requested or left blank to get the default feed.
  *
- * @package WordPress
- * @subpackage Feed
  * @since 2.5.0
  *
  * @param int $cat_id ID of a category.
@@ -578,7 +750,7 @@
  * Returns a link to the feed for all posts in a given term. A specific feed
  * can be requested or left blank to get the default feed.
  *
- * @since 3.0
+ * @since 3.0.0
  *
  * @param int $term_id ID of a category.
  * @param string $taxonomy Optional. Taxonomy of $term_id
@@ -618,12 +790,38 @@
 		$link = trailingslashit( $link ) . user_trailingslashit( $feed_link, 'feed' );
 	}
 
-	if ( 'category' == $taxonomy )
+	if ( 'category' == $taxonomy ) {
+		/**
+		 * Filter the category feed link.
+		 *
+		 * @since 1.5.1
+		 *
+		 * @param string $link The category feed link.
+		 * @param string $feed Feed type.
+		 */
 		$link = apply_filters( 'category_feed_link', $link, $feed );
-	elseif ( 'post_tag' == $taxonomy )
+	} elseif ( 'post_tag' == $taxonomy ) {
+		/**
+		 * Filter the post tag feed link.
+		 *
+		 * @since 2.3.0
+		 *
+		 * @param string $link The tag feed link.
+		 * @param string $feed Feed type.
+		 */
 		$link = apply_filters( 'tag_feed_link', $link, $feed );
-	else
+	} else {
+		/**
+		 * Filter the feed link for a taxonomy other than 'category' or 'post_tag'.
+		 *
+		 * @since 3.0.0
+		 *
+		 * @param string $link The taxonomy feed link.
+		 * @param string $feed Feed type.
+		 * @param string $feed The taxonomy name.
+		 */
 		$link = apply_filters( 'taxonomy_feed_link', $link, $feed, $taxonomy );
+	}
 
 	return $link;
 }
@@ -635,7 +833,7 @@
  *
  * @param int $tag_id Tag ID.
  * @param string $feed Optional. Feed type.
- * @return string
+ * @return string The feed permalink for the given tag.
  */
 function get_tag_feed_link($tag_id, $feed = '') {
 	return get_term_feed_link($tag_id, 'post_tag', $feed);
@@ -648,9 +846,16 @@
  *
  * @param int $tag_id Tag ID
  * @param string $taxonomy Taxonomy
- * @return string
+ * @return string The edit tag link URL for the given tag.
  */
 function get_edit_tag_link( $tag_id, $taxonomy = 'post_tag' ) {
+	/**
+	 * Filter the edit link for a tag (or term in another taxonomy).
+	 *
+	 * @since 2.7.0
+	 *
+	 * @param string $link The term edit link.
+	 */
 	return apply_filters( 'get_edit_tag_link', get_edit_term_link( $tag_id, $taxonomy ) );
 }
 
@@ -667,6 +872,14 @@
  */
 function edit_tag_link( $link = '', $before = '', $after = '', $tag = null ) {
 	$link = edit_term_link( $link, '', '', $tag, false );
+
+	/**
+	 * Filter the anchor tag for the edit link for a tag (or term in another taxonomy).
+	 *
+	 * @since 2.7.0
+	 *
+	 * @param string $link The anchor tag for the edit link.
+	 */
 	echo $before . apply_filters( 'edit_tag_link', $link ) . $after;
 }
 
@@ -675,10 +888,11 @@
  *
  * @since 3.1.0
  *
- * @param int $term_id Term ID
- * @param string $taxonomy Taxonomy
- * @param string $object_type The object type
- * @return string
+ * @param int    $term_id     Term ID.
+ * @param string $taxonomy    Taxonomy.
+ * @param string $object_type The object type. Used to highlight the proper post type menu on the linked page.
+ *                            Defaults to the first object_type associated with the taxonomy.
+ * @return string The edit term link URL for the given term.
  */
 function get_edit_term_link( $term_id, $taxonomy, $object_type = '' ) {
 	$tax = get_taxonomy( $taxonomy );
@@ -693,11 +907,24 @@
 		'tag_ID' => $term->term_id,
 	);
 
-	if ( $object_type )
+	if ( $object_type ) {
 		$args['post_type'] = $object_type;
+	} else if ( ! empty( $tax->object_type ) ) {
+		$args['post_type'] = reset( $tax->object_type );
+	}
 
 	$location = add_query_arg( $args, admin_url( 'edit-tags.php' ) );
 
+	/**
+	 * Filter the edit link for a term.
+	 *
+	 * @since 3.1.0
+	 *
+	 * @param string $location    The edit link.
+	 * @param int    $term_id     Term ID.
+	 * @param string $taxonomy    Taxonomy name.
+	 * @param string $object_type The object type (eg. the post type).
+	 */
 	return apply_filters( 'get_edit_term_link', $location, $term_id, $taxonomy, $object_type );
 }
 
@@ -727,6 +954,15 @@
 		$link = __('Edit This');
 
 	$link = '<a href="' . get_edit_term_link( $term->term_id, $term->taxonomy ) . '">' . $link . '</a>';
+
+	/**
+	 * Filter the anchor tag for the edit link of a term.
+	 *
+	 * @since 3.1.0
+	 *
+	 * @param string $link    The anchor tag for the edit link.
+	 * @param int    $term_id Term ID.
+	 */
 	$link = $before . apply_filters( 'edit_term_link', $link, $term->term_id ) . $after;
 
 	if ( $echo )
@@ -736,12 +972,13 @@
 }
 
 /**
-* Retrieve permalink for search.
-*
-* @since  3.0.0
-* @param string $query Optional. The query string to use. If empty the current query is used.
-* @return string
-*/
+ * Retrieve permalink for search.
+ *
+ * @since  3.0.0
+ *
+ * @param string $query Optional. The query string to use. If empty the current query is used.
+ * @return string The search permalink.
+ */
 function get_search_link( $query = '' ) {
 	global $wp_rewrite;
 
@@ -761,6 +998,14 @@
 		$link = home_url( user_trailingslashit( $link, 'search' ) );
 	}
 
+	/**
+	 * Filter the search permalink.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param string $link   Search permalink.
+	 * @param string $search The URL-encoded search term.
+	 */
 	return apply_filters( 'search_link', $link, $search );
 }
 
@@ -771,7 +1016,7 @@
  *
  * @param string $search_query Optional. Search query.
  * @param string $feed Optional. Feed type.
- * @return string
+ * @return string The search results feed permalink.
  */
 function get_search_feed_link($search_query = '', $feed = '') {
 	global $wp_rewrite;
@@ -789,7 +1034,16 @@
 		$link .= "feed/$feed/";
 	}
 
-	$link = apply_filters('search_feed_link', $link, $feed, 'posts');
+	/**
+	 * Filter the search feed link.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param string $link Search feed link.
+	 * @param string $feed Feed type.
+	 * @param string $type The search type. One of 'posts' or 'comments'.
+	 */
+	$link = apply_filters( 'search_feed_link', $link, $feed, 'posts' );
 
 	return $link;
 }
@@ -801,7 +1055,7 @@
  *
  * @param string $search_query Optional. Search query.
  * @param string $feed Optional. Feed type.
- * @return string
+ * @return string The comments feed search results permalink.
  */
 function get_search_comments_feed_link($search_query = '', $feed = '') {
 	global $wp_rewrite;
@@ -818,6 +1072,7 @@
 	else
 		$link = add_query_arg('withcomments', 1, $link);
 
+	/** This filter is documented in wp-includes/link-template.php */
 	$link = apply_filters('search_feed_link', $link, $feed, 'comments');
 
 	return $link;
@@ -829,7 +1084,7 @@
  * @since 3.1.0
  *
  * @param string $post_type Post type
- * @return string
+ * @return string The post type archive permalink.
  */
 function get_post_type_archive_link( $post_type ) {
 	global $wp_rewrite;
@@ -850,6 +1105,14 @@
 		$link = home_url( '?post_type=' . $post_type );
 	}
 
+	/**
+	 * Filter the post type archive permalink.
+	 *
+	 * @since 3.1.0
+	 *
+	 * @param string $link      The post type archive permalink.
+	 * @param string $post_type Post type name.
+	 */
 	return apply_filters( 'post_type_archive_link', $link, $post_type );
 }
 
@@ -860,7 +1123,7 @@
  *
  * @param string $post_type Post type
  * @param string $feed Optional. Feed type
- * @return string
+ * @return string The post type feed permalink.
  */
 function get_post_type_archive_feed_link( $post_type, $feed = '' ) {
 	$default_feed = get_default_feed();
@@ -880,6 +1143,14 @@
 		$link = add_query_arg( 'feed', $feed, $link );
 	}
 
+	/**
+	 * Filter the post type archive feed link.
+	 *
+	 * @since 3.1.0
+	 *
+	 * @param string $link The post type archive feed link.
+	 * @param string $feed Feed type.
+	 */
 	return apply_filters( 'post_type_archive_feed_link', $link, $feed );
 }
 
@@ -893,7 +1164,7 @@
  *
  * @param int $id Optional. Post ID.
  * @param string $context Optional, defaults to display. How to write the '&', defaults to '&amp;'.
- * @return string
+ * @return string The edit post link for the given post.
  */
 function get_edit_post_link( $id = 0, $context = 'display' ) {
 	if ( ! $post = get_post( $id ) )
@@ -913,7 +1184,17 @@
 	if ( !current_user_can( 'edit_post', $post->ID ) )
 		return;
 
-	return apply_filters( 'get_edit_post_link', admin_url( sprintf($post_type_object->_edit_link . $action, $post->ID) ), $post->ID, $context );
+	/**
+	 * Filter the post edit link.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param string $link    The edit link.
+	 * @param int    $post_id Post ID.
+	 * @param string $context The link context. If set to 'display' then ampersands
+	 *                        are encoded.
+	 */
+	return apply_filters( 'get_edit_post_link', admin_url( sprintf( $post_type_object->_edit_link . $action, $post->ID ) ), $post->ID, $context );
 }
 
 /**
@@ -921,24 +1202,36 @@
  *
  * @since 1.0.0
  *
- * @param string $link Optional. Anchor text.
+ * @param string $text Optional. Anchor text.
  * @param string $before Optional. Display before edit link.
  * @param string $after Optional. Display after edit link.
  * @param int $id Optional. Post ID.
  */
-function edit_post_link( $link = null, $before = '', $after = '', $id = 0 ) {
-	if ( !$post = get_post( $id ) )
+function edit_post_link( $text = null, $before = '', $after = '', $id = 0 ) {
+	if ( ! $post = get_post( $id ) ) {
 		return;
-
-	if ( !$url = get_edit_post_link( $post->ID ) )
+	}
+
+	if ( ! $url = get_edit_post_link( $post->ID ) ) {
 		return;
-
-	if ( null === $link )
-		$link = __('Edit This');
-
-	$post_type_obj = get_post_type_object( $post->post_type );
-	$link = '<a class="post-edit-link" href="' . $url . '">' . $link . '</a>';
-	echo $before . apply_filters( 'edit_post_link', $link, $post->ID ) . $after;
+	}
+
+	if ( null === $text ) {
+		$text = __( 'Edit This' );
+	}
+
+	$link = '<a class="post-edit-link" href="' . $url . '">' . $text . '</a>';
+
+	/**
+	 * Filter the post edit link anchor tag.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param string $link    Anchor tag for the edit link.
+	 * @param int    $post_id Post ID.
+	 * @param string $text    Anchor text.
+	 */
+	echo $before . apply_filters( 'edit_post_link', $link, $post->ID, $text ) . $after;
 }
 
 /**
@@ -951,7 +1244,7 @@
  * @param int $id Optional. Post ID.
  * @param string $deprecated Not used.
  * @param bool $force_delete Whether to bypass trash and force deletion. Default is false.
- * @return string
+ * @return string The delete post link URL for the given post.
  */
 function get_delete_post_link( $id = 0, $deprecated = '', $force_delete = false ) {
 	if ( ! empty( $deprecated ) )
@@ -971,6 +1264,15 @@
 
 	$delete_link = add_query_arg( 'action', $action, admin_url( sprintf( $post_type_object->_edit_link, $post->ID ) ) );
 
+	/**
+	 * Filter the post delete link.
+	 *
+	 * @since 2.9.0
+	 *
+	 * @param string $link         The delete link.
+	 * @param int    $post_id      Post ID.
+	 * @param bool   $force_delete Whether to bypass the trash and force deletion. Default false.
+	 */
 	return apply_filters( 'get_delete_post_link', wp_nonce_url( $delete_link, "$action-post_{$post->ID}" ), $post->ID, $force_delete );
 }
 
@@ -980,7 +1282,7 @@
  * @since 2.3.0
  *
  * @param int $comment_id Optional. Comment ID.
- * @return string
+ * @return string The edit comment link URL for the given comment.
  */
 function get_edit_comment_link( $comment_id = 0 ) {
 	$comment = get_comment( $comment_id );
@@ -989,30 +1291,49 @@
 		return;
 
 	$location = admin_url('comment.php?action=editcomment&amp;c=') . $comment->comment_ID;
+
+	/**
+	 * Filter the comment edit link.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param string $location The edit link.
+	 */
 	return apply_filters( 'get_edit_comment_link', $location );
 }
 
 /**
- * Display or retrieve edit comment link with formatting.
+ * Display edit comment link with formatting.
  *
  * @since 1.0.0
  *
- * @param string $link Optional. Anchor text.
+ * @param string $text Optional. Anchor text.
  * @param string $before Optional. Display before edit link.
  * @param string $after Optional. Display after edit link.
- * @return string|null HTML content, if $echo is set to false.
  */
-function edit_comment_link( $link = null, $before = '', $after = '' ) {
+function edit_comment_link( $text = null, $before = '', $after = '' ) {
 	global $comment;
 
-	if ( !current_user_can( 'edit_comment', $comment->comment_ID ) )
+	if ( ! current_user_can( 'edit_comment', $comment->comment_ID ) ) {
 		return;
-
-	if ( null === $link )
-		$link = __('Edit This');
-
-	$link = '<a class="comment-edit-link" href="' . get_edit_comment_link( $comment->comment_ID ) . '">' . $link . '</a>';
-	echo $before . apply_filters( 'edit_comment_link', $link, $comment->comment_ID ) . $after;
+	}
+
+	if ( null === $text ) {
+		$text = __( 'Edit This' );
+	}
+
+	$link = '<a class="comment-edit-link" href="' . get_edit_comment_link( $comment->comment_ID ) . '">' . $text . '</a>';
+
+	/**
+	 * Filter the comment edit link anchor tag.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param string $link       Anchor tag for the edit link.
+	 * @param int    $comment_id Comment ID.
+	 * @param string $text       Anchor text.
+	 */
+	echo $before . apply_filters( 'edit_comment_link', $link, $comment->comment_ID, $text ) . $after;
 }
 
 /**
@@ -1020,8 +1341,8 @@
  *
  * @since 2.7.0
  *
- * @param int $link Optional. Bookmark ID.
- * @return string
+ * @param int|stdClass $link Optional. Bookmark ID.
+ * @return string The edit bookmark link URL.
  */
 function get_edit_bookmark_link( $link = 0 ) {
 	$link = get_bookmark( $link );
@@ -1030,6 +1351,15 @@
 		return;
 
 	$location = admin_url('link.php?action=edit&amp;link_id=') . $link->link_id;
+
+	/**
+	 * Filter the bookmark (link) edit link.
+	 *
+	 * @since 2.7.0
+	 *
+	 * @param string $location The edit link.
+	 * @param int    $link_id  Bookmark ID.
+	 */
 	return apply_filters( 'get_edit_bookmark_link', $location, $link->link_id );
 }
 
@@ -1053,6 +1383,15 @@
 		$link = __('Edit This');
 
 	$link = '<a href="' . get_edit_bookmark_link( $bookmark ) . '">' . $link . '</a>';
+
+	/**
+	 * Filter the bookmark edit link anchor tag.
+	 *
+	 * @since 2.7.0
+	 *
+	 * @param string $link    Anchor tag for the edit link.
+	 * @param int    $link_id Bookmark ID.
+	 */
 	echo $before . apply_filters( 'edit_bookmark_link', $link, $bookmark->link_id ) . $after;
 }
 
@@ -1081,6 +1420,14 @@
 	else
 		$link = add_query_arg( 'user_id', $user->ID, self_admin_url( 'user-edit.php' ) );
 
+	/**
+	 * Filter the user edit link.
+	 *
+	 * @since 3.5.0
+	 *
+	 * @param string $link    The edit link.
+	 * @param int    $user_id User ID.
+	 */
 	return apply_filters( 'get_edit_user_link', $link, $user->ID );
 }
 
@@ -1091,12 +1438,13 @@
  *
  * @since 1.5.0
  *
- * @param bool $in_same_cat Optional. Whether post should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
- * @return mixed Post object if successful. Null if global $post is not set. Empty string if no corresponding post exists.
+ * @param bool         $in_same_term   Optional. Whether post should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
+ * @return mixed       Post object if successful. Null if global $post is not set. Empty string if no corresponding post exists.
  */
-function get_previous_post($in_same_cat = false, $excluded_categories = '') {
-	return get_adjacent_post($in_same_cat, $excluded_categories);
+function get_previous_post( $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' ) {
+	return get_adjacent_post( $in_same_term, $excluded_terms, true, $taxonomy );
 }
 
 /**
@@ -1104,12 +1452,13 @@
  *
  * @since 1.5.0
  *
- * @param bool $in_same_cat Optional. Whether post should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
- * @return mixed Post object if successful. Null if global $post is not set. Empty string if no corresponding post exists.
+ * @param bool         $in_same_term   Optional. Whether post should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
+ * @return mixed       Post object if successful. Null if global $post is not set. Empty string if no corresponding post exists.
  */
-function get_next_post($in_same_cat = false, $excluded_categories = '') {
-	return get_adjacent_post($in_same_cat, $excluded_categories, false);
+function get_next_post( $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' ) {
+	return get_adjacent_post( $in_same_term, $excluded_terms, false, $taxonomy );
 }
 
 /**
@@ -1119,69 +1468,136 @@
  *
  * @since 2.5.0
  *
- * @param bool $in_same_cat Optional. Whether post should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
- * @param bool $previous Optional. Whether to retrieve previous post.
- * @return mixed Post object if successful. Null if global $post is not set. Empty string if no corresponding post exists.
+ * @param bool         $in_same_term   Optional. Whether post should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
+ * @param bool         $previous       Optional. Whether to retrieve previous post.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
+ * @return mixed       Post object if successful. Null if global $post is not set. Empty string if no corresponding post exists.
  */
-function get_adjacent_post( $in_same_cat = false, $excluded_categories = '', $previous = true ) {
+function get_adjacent_post( $in_same_term = false, $excluded_terms = '', $previous = true, $taxonomy = 'category' ) {
 	global $wpdb;
 
-	if ( ! $post = get_post() )
+	if ( ( ! $post = get_post() ) || ! taxonomy_exists( $taxonomy ) )
 		return null;
 
 	$current_post_date = $post->post_date;
 
 	$join = '';
-	$posts_in_ex_cats_sql = '';
-	if ( $in_same_cat || ! empty( $excluded_categories ) ) {
+	$where = '';
+
+	if ( $in_same_term || ! empty( $excluded_terms ) ) {
 		$join = " INNER JOIN $wpdb->term_relationships AS tr ON p.ID = tr.object_id INNER JOIN $wpdb->term_taxonomy tt ON tr.term_taxonomy_id = tt.term_taxonomy_id";
-
-		if ( $in_same_cat ) {
-			if ( ! is_object_in_taxonomy( $post->post_type, 'category' ) )
-				return '';
-			$cat_array = wp_get_object_terms($post->ID, 'category', array('fields' => 'ids'));
-			if ( ! $cat_array || is_wp_error( $cat_array ) )
-				return '';
-			$join .= " AND tt.taxonomy = 'category' AND tt.term_id IN (" . implode(',', $cat_array) . ")";
+		$where = $wpdb->prepare( "AND tt.taxonomy = %s", $taxonomy );
+
+		if ( ! empty( $excluded_terms ) && ! is_array( $excluded_terms ) ) {
+			// back-compat, $excluded_terms used to be $excluded_terms with IDs separated by " and "
+			if ( false !== strpos( $excluded_terms, ' and ' ) ) {
+				_deprecated_argument( __FUNCTION__, '3.3', sprintf( __( 'Use commas instead of %s to separate excluded terms.' ), "'and'" ) );
+				$excluded_terms = explode( ' and ', $excluded_terms );
+			} else {
+				$excluded_terms = explode( ',', $excluded_terms );
+			}
+
+			$excluded_terms = array_map( 'intval', $excluded_terms );
 		}
 
-		$posts_in_ex_cats_sql = "AND tt.taxonomy = 'category'";
-		if ( ! empty( $excluded_categories ) ) {
-			if ( ! is_array( $excluded_categories ) ) {
-				// back-compat, $excluded_categories used to be IDs separated by " and "
-				if ( strpos( $excluded_categories, ' and ' ) !== false ) {
-					_deprecated_argument( __FUNCTION__, '3.3', sprintf( __( 'Use commas instead of %s to separate excluded categories.' ), "'and'" ) );
-					$excluded_categories = explode( ' and ', $excluded_categories );
-				} else {
-					$excluded_categories = explode( ',', $excluded_categories );
-				}
-			}
-
-			$excluded_categories = array_map( 'intval', $excluded_categories );
-
-			if ( ! empty( $cat_array ) ) {
-				$excluded_categories = array_diff($excluded_categories, $cat_array);
-				$posts_in_ex_cats_sql = '';
-			}
-
-			if ( !empty($excluded_categories) ) {
-				$posts_in_ex_cats_sql = " AND tt.taxonomy = 'category' AND tt.term_id NOT IN (" . implode($excluded_categories, ',') . ')';
+		if ( $in_same_term ) {
+			if ( ! is_object_in_taxonomy( $post->post_type, $taxonomy ) )
+				return '';
+			$term_array = wp_get_object_terms( $post->ID, $taxonomy, array( 'fields' => 'ids' ) );
+
+			// Remove any exclusions from the term array to include.
+			$term_array = array_diff( $term_array, (array) $excluded_terms );
+			$term_array = array_map( 'intval', $term_array );
+
+			if ( ! $term_array || is_wp_error( $term_array ) )
+				return '';
+
+			$where .= " AND tt.term_id IN (" . implode( ',', $term_array ) . ")";
+		}
+
+		if ( ! empty( $excluded_terms ) ) {
+			$where .= " AND p.ID NOT IN ( SELECT tr.object_id FROM $wpdb->term_relationships tr LEFT JOIN $wpdb->term_taxonomy tt ON (tr.term_taxonomy_id = tt.term_taxonomy_id) WHERE tt.term_id IN (" . implode( $excluded_terms, ',' ) . ') )';
+		}
+	}
+
+	// 'post_status' clause depends on the current user.
+	if ( is_user_logged_in() ) {
+		$user_id = get_current_user_id();
+
+		$post_type_object = get_post_type_object( $post->post_type );
+		if ( empty( $post_type_object ) ) {
+			$post_type_cap    = $post->post_type;
+			$read_private_cap = 'read_private_' . $post_type_cap . 's';
+		} else {
+			$read_private_cap = $post_type_object->cap->read_private_posts;
+		}
+
+		/*
+		 * Results should include private posts belonging to the current user, or private posts where the
+		 * current user has the 'read_private_posts' cap.
+		 */
+		$private_states = get_post_stati( array( 'private' => true ) );
+		$where .= " AND ( p.post_status = 'publish'";
+		foreach ( (array) $private_states as $state ) {
+			if ( current_user_can( $read_private_cap ) ) {
+				$where .= $wpdb->prepare( " OR p.post_status = %s", $state );
+			} else {
+				$where .= $wpdb->prepare( " OR (p.post_author = %d AND p.post_status = %s)", $user_id, $state );
 			}
 		}
+		$where .= " )";
+	} else {
+		$where .= " AND p.post_status = 'publish'";
 	}
 
 	$adjacent = $previous ? 'previous' : 'next';
 	$op = $previous ? '<' : '>';
 	$order = $previous ? 'DESC' : 'ASC';
 
-	$join  = apply_filters( "get_{$adjacent}_post_join", $join, $in_same_cat, $excluded_categories );
-	$where = apply_filters( "get_{$adjacent}_post_where", $wpdb->prepare("WHERE p.post_date $op %s AND p.post_type = %s AND p.post_status = 'publish' $posts_in_ex_cats_sql", $current_post_date, $post->post_type), $in_same_cat, $excluded_categories );
+	/**
+	 * Filter the JOIN clause in the SQL for an adjacent post query.
+	 *
+	 * The dynamic portion of the hook name, `$adjacent`, refers to the type
+	 * of adjacency, 'next' or 'previous'.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param string $join           The JOIN clause in the SQL.
+	 * @param bool   $in_same_term   Whether post should be in a same taxonomy term.
+	 * @param array  $excluded_terms Array of excluded term IDs.
+	 */
+	$join  = apply_filters( "get_{$adjacent}_post_join", $join, $in_same_term, $excluded_terms );
+
+	/**
+	 * Filter the WHERE clause in the SQL for an adjacent post query.
+	 *
+	 * The dynamic portion of the hook name, `$adjacent`, refers to the type
+	 * of adjacency, 'next' or 'previous'.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param string $where          The `WHERE` clause in the SQL.
+	 * @param bool   $in_same_term   Whether post should be in a same taxonomy term.
+	 * @param array  $excluded_terms Array of excluded term IDs.
+	 */
+	$where = apply_filters( "get_{$adjacent}_post_where", $wpdb->prepare( "WHERE p.post_date $op %s AND p.post_type = %s $where", $current_post_date, $post->post_type ), $in_same_term, $excluded_terms );
+
+	/**
+	 * Filter the ORDER BY clause in the SQL for an adjacent post query.
+	 *
+	 * The dynamic portion of the hook name, `$adjacent`, refers to the type
+	 * of adjacency, 'next' or 'previous'.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param string $order_by The `ORDER BY` clause in the SQL.
+	 */
 	$sort  = apply_filters( "get_{$adjacent}_post_sort", "ORDER BY p.post_date $order LIMIT 1" );
 
 	$query = "SELECT p.ID FROM $wpdb->posts AS p $join $where $sort";
-	$query_key = 'adjacent_post_' . md5($query);
-	$result = wp_cache_get($query_key, 'counts');
+	$query_key = 'adjacent_post_' . md5( $query );
+	$result = wp_cache_get( $query_key, 'counts' );
 	if ( false !== $result ) {
 		if ( $result )
 			$result = get_post( $result );
@@ -1192,7 +1608,7 @@
 	if ( null === $result )
 		$result = '';
 
-	wp_cache_set($query_key, $result, 'counts');
+	wp_cache_set( $query_key, $result, 'counts' );
 
 	if ( $result )
 		$result = get_post( $result );
@@ -1207,36 +1623,48 @@
  *
  * @since 2.8.0
  *
- * @param string $title Optional. Link title format.
- * @param bool $in_same_cat Optional. Whether link should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
- * @param bool $previous Optional, default is true. Whether to display link to previous or next post.
- * @return string
+ * @param string       $title          Optional. Link title format.
+ * @param bool         $in_same_term   Optional. Whether link should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
+ * @param bool         $previous       Optional. Whether to display link to previous or next post. Default true.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
+ * @return string The adjacent post relational link URL.
  */
-function get_adjacent_post_rel_link($title = '%title', $in_same_cat = false, $excluded_categories = '', $previous = true) {
+function get_adjacent_post_rel_link( $title = '%title', $in_same_term = false, $excluded_terms = '', $previous = true, $taxonomy = 'category' ) {
 	if ( $previous && is_attachment() && $post = get_post() )
 		$post = get_post( $post->post_parent );
 	else
-		$post = get_adjacent_post( $in_same_cat, $excluded_categories, $previous );
-
-	if ( empty($post) )
+		$post = get_adjacent_post( $in_same_term, $excluded_terms, $previous, $taxonomy );
+
+	if ( empty( $post ) )
 		return;
 
 	$post_title = the_title_attribute( array( 'echo' => false, 'post' => $post ) );
 
 	if ( empty( $post_title ) )
-		$post_title = $previous ? __('Previous Post') : __('Next Post');
-
-	$date = mysql2date(get_option('date_format'), $post->post_date);
-
-	$title = str_replace('%title', $post_title, $title);
-	$title = str_replace('%date', $date, $title);
+		$post_title = $previous ? __( 'Previous Post' ) : __( 'Next Post' );
+
+	$date = mysql2date( get_option( 'date_format' ), $post->post_date );
+
+	$title = str_replace( '%title', $post_title, $title );
+	$title = str_replace( '%date', $date, $title );
 
 	$link = $previous ? "<link rel='prev' title='" : "<link rel='next' title='";
 	$link .= esc_attr( $title );
-	$link .= "' href='" . get_permalink($post) . "' />\n";
+	$link .= "' href='" . get_permalink( $post ) . "' />\n";
 
 	$adjacent = $previous ? 'previous' : 'next';
+
+	/**
+	 * Filter the adjacent post relational link.
+	 *
+	 * The dynamic portion of the hook name, `$adjacent`, refers to the type
+	 * of adjacency, 'next' or 'previous'.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @param string $link The relational link.
+	 */
 	return apply_filters( "{$adjacent}_post_rel_link", $link );
 }
 
@@ -1245,13 +1673,14 @@
  *
  * @since 2.8.0
  *
- * @param string $title Optional. Link title format.
- * @param bool $in_same_cat Optional. Whether link should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
+ * @param string       $title          Optional. Link title format.
+ * @param bool         $in_same_term   Optional. Whether link should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
  */
-function adjacent_posts_rel_link($title = '%title', $in_same_cat = false, $excluded_categories = '') {
-	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories = '', true);
-	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories = '', false);
+function adjacent_posts_rel_link( $title = '%title', $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' ) {
+	echo get_adjacent_post_rel_link( $title, $in_same_term, $excluded_terms, true, $taxonomy );
+	echo get_adjacent_post_rel_link( $title, $in_same_term, $excluded_terms, false, $taxonomy );
 }
 
 /**
@@ -1262,8 +1691,9 @@
  *
  */
 function adjacent_posts_rel_link_wp_head() {
-	if ( !is_singular() || is_attachment() )
+	if ( ! is_single() || is_attachment() ) {
 		return;
+	}
 	adjacent_posts_rel_link();
 }
 
@@ -1272,12 +1702,13 @@
  *
  * @since 2.8.0
  *
- * @param string $title Optional. Link title format.
- * @param bool $in_same_cat Optional. Whether link should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
+ * @param string       $title          Optional. Link title format.
+ * @param bool         $in_same_term   Optional. Whether link should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
  */
-function next_post_rel_link($title = '%title', $in_same_cat = false, $excluded_categories = '') {
-	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories = '', false);
+function next_post_rel_link( $title = '%title', $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' ) {
+	echo get_adjacent_post_rel_link( $title, $in_same_term, $excluded_terms, false, $taxonomy );
 }
 
 /**
@@ -1285,56 +1716,71 @@
  *
  * @since 2.8.0
  *
- * @param string $title Optional. Link title format.
- * @param bool $in_same_cat Optional. Whether link should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
+ * @param string       $title          Optional. Link title format.
+ * @param bool         $in_same_term   Optional. Whether link should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs. Default true.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
  */
-function prev_post_rel_link($title = '%title', $in_same_cat = false, $excluded_categories = '') {
-	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories = '', true);
+function prev_post_rel_link( $title = '%title', $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' ) {
+	echo get_adjacent_post_rel_link( $title, $in_same_term, $excluded_terms, true, $taxonomy );
 }
 
 /**
  * Retrieve boundary post.
  *
  * Boundary being either the first or last post by publish date within the constraints specified
- * by $in_same_cat or $excluded_categories.
+ * by $in_same_term or $excluded_terms.
  *
  * @since 2.8.0
  *
- * @param bool $in_same_cat Optional. Whether returned post should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
- * @param bool $start Optional. Whether to retrieve first or last post.
- * @return object
+ * @param bool         $in_same_term   Optional. Whether returned post should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
+ * @param bool         $start          Optional. Whether to retrieve first or last post.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
+ * @return mixed Array containing the boundary post object if successful, null otherwise.
  */
-function get_boundary_post( $in_same_cat = false, $excluded_categories = '', $start = true ) {
+function get_boundary_post( $in_same_term = false, $excluded_terms = '', $start = true, $taxonomy = 'category' ) {
 	$post = get_post();
-	if ( ! $post || ! is_single() || is_attachment() )
+	if ( ! $post || ! is_single() || is_attachment() || ! taxonomy_exists( $taxonomy ) )
 		return null;
 
-	$cat_array = array();
-	if( ! is_array( $excluded_categories ) )
-		$excluded_categories = explode( ',', $excluded_categories );
-
-	if ( $in_same_cat || ! empty( $excluded_categories ) ) {
-		if ( $in_same_cat )
-			$cat_array = wp_get_object_terms( $post->ID, 'category', array( 'fields' => 'ids' ) );
-
-		if ( ! empty( $excluded_categories ) ) {
-			$excluded_categories = array_map( 'intval', $excluded_categories );
-			$excluded_categories = array_diff( $excluded_categories, $cat_array );
-
-			$inverse_cats = array();
-			foreach ( $excluded_categories as $excluded_category )
-				$inverse_cats[] = $excluded_category * -1;
-			$excluded_categories = $inverse_cats;
+	$query_args = array(
+		'posts_per_page' => 1,
+		'order' => $start ? 'ASC' : 'DESC',
+		'update_post_term_cache' => false,
+		'update_post_meta_cache' => false
+	);
+
+	$term_array = array();
+
+	if ( ! is_array( $excluded_terms ) ) {
+		if ( ! empty( $excluded_terms ) )
+			$excluded_terms = explode( ',', $excluded_terms );
+		else
+			$excluded_terms = array();
+	}
+
+	if ( $in_same_term || ! empty( $excluded_terms ) ) {
+		if ( $in_same_term )
+			$term_array = wp_get_object_terms( $post->ID, $taxonomy, array( 'fields' => 'ids' ) );
+
+		if ( ! empty( $excluded_terms ) ) {
+			$excluded_terms = array_map( 'intval', $excluded_terms );
+			$excluded_terms = array_diff( $excluded_terms, $term_array );
+
+			$inverse_terms = array();
+			foreach ( $excluded_terms as $excluded_term )
+				$inverse_terms[] = $excluded_term * -1;
+			$excluded_terms = $inverse_terms;
 		}
+
+		$query_args[ 'tax_query' ] = array( array(
+			'taxonomy' => $taxonomy,
+			'terms' => array_merge( $term_array, $excluded_terms )
+		) );
 	}
 
-	$categories = implode( ',', array_merge( $cat_array, $excluded_categories ) );
-
-	$order = $start ? 'ASC' : 'DESC';
-
-	return get_posts( array('numberposts' => 1, 'category' => $categories, 'order' => $order, 'update_post_term_cache' => false, 'update_post_meta_cache' => false) );
+	return get_posts( $query_args );
 }
 
 /*
@@ -1342,59 +1788,63 @@
  *
  * @since 3.7.0
  *
- * @param string $format Optional. Link anchor format.
- * @param string $link Optional. Link permalink format.
- * @param bool $in_same_cat Optional. Whether link should be in same category.
- * @param string $excluded_categories Optional. Excluded categories IDs.
- * @return string
+ * @param string       $format         Optional. Link anchor format.
+ * @param string       $link           Optional. Link permalink format.
+ * @param bool         $in_same_term   Optional. Whether link should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
+ * @return string The link URL of the previous post in relation to the current post.
  */
-function get_previous_post_link( $format = '&laquo; %link', $link = '%title', $in_same_cat = false, $excluded_categories = '' ) {
-	return get_adjacent_post_link( $format, $link, $in_same_cat, $excluded_categories, true );
+function get_previous_post_link( $format = '&laquo; %link', $link = '%title', $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' ) {
+	return get_adjacent_post_link( $format, $link, $in_same_term, $excluded_terms, true, $taxonomy );
 }
 
 /**
  * Display previous post link that is adjacent to the current post.
  *
  * @since 1.5.0
- * @uses get_previous_post_link()
+ * @see get_previous_post_link()
  *
- * @param string $format Optional. Link anchor format.
- * @param string $link Optional. Link permalink format.
- * @param bool $in_same_cat Optional. Whether link should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
+ * @param string       $format         Optional. Link anchor format.
+ * @param string       $link           Optional. Link permalink format.
+ * @param bool         $in_same_term   Optional. Whether link should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
  */
-function previous_post_link( $format = '&laquo; %link', $link = '%title', $in_same_cat = false, $excluded_categories = '' ) {
-	echo get_previous_post_link( $format, $link, $in_same_cat, $excluded_categories );
+function previous_post_link( $format = '&laquo; %link', $link = '%title', $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' ) {
+	echo get_previous_post_link( $format, $link, $in_same_term, $excluded_terms, $taxonomy );
 }
 
 /**
- * Get previous post link that is adjacent to the current post.
+ * Get next post link that is adjacent to the current post.
  *
  * @since 3.7.0
- * @uses get_next_post_link()
  *
- * @param string $format Optional. Link anchor format.
- * @param string $link Optional. Link permalink format.
- * @param bool $in_same_cat Optional. Whether link should be in same category.
- * @param string $excluded_categories Optional. Excluded categories IDs.
- * @return string
+ * @param string       $format         Optional. Link anchor format.
+ * @param string       $link           Optional. Link permalink format.
+ * @param bool         $in_same_term   Optional. Whether link should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
+ * @return string The link URL of the next post in relation to the current post.
  */
-function get_next_post_link( $format = '&laquo; %link', $link = '%title', $in_same_cat = false, $excluded_categories = '' ) {
-	return get_adjacent_post_link( $format, $link, $in_same_cat, $excluded_categories, false );
+function get_next_post_link( $format = '%link &raquo;', $link = '%title', $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' ) {
+	return get_adjacent_post_link( $format, $link, $in_same_term, $excluded_terms, false, $taxonomy );
 }
 
 /**
  * Display next post link that is adjacent to the current post.
  *
  * @since 1.5.0
+ * @see get_next_post_link()
  *
- * @param string $format Optional. Link anchor format.
- * @param string $link Optional. Link permalink format.
- * @param bool $in_same_cat Optional. Whether link should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
+ * @param string       $format         Optional. Link anchor format.
+ * @param string       $link           Optional. Link permalink format.
+ * @param bool         $in_same_term   Optional. Whether link should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
  */
-function next_post_link( $format = '%link &raquo;', $link = '%title', $in_same_cat = false, $excluded_categories = '' ) {
-	 echo get_next_post_link( $format, $link, $in_same_cat, $excluded_categories );
+function next_post_link( $format = '%link &raquo;', $link = '%title', $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' ) {
+	 echo get_next_post_link( $format, $link, $in_same_term, $excluded_terms, $taxonomy );
 }
 
 /**
@@ -1404,18 +1854,19 @@
  *
  * @since 3.7.0
  *
- * @param string $format Link anchor format.
- * @param string $link Link permalink format.
- * @param bool $in_same_cat Optional. Whether link should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
- * @param bool $previous Optional, default is true. Whether to display link to previous or next post.
- * @return string
+ * @param string       $format         Link anchor format.
+ * @param string       $link           Link permalink format.
+ * @param bool         $in_same_term   Optional. Whether link should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded terms IDs.
+ * @param bool         $previous       Optional. Whether to display link to previous or next post. Default true.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
+ * @return string The link URL of the previous or next post in relation to the current post.
  */
-function get_adjacent_post_link( $format, $link, $in_same_cat = false, $excluded_categories = '', $previous = true ) {
+function get_adjacent_post_link( $format, $link, $in_same_term = false, $excluded_terms = '', $previous = true, $taxonomy = 'category' ) {
 	if ( $previous && is_attachment() )
 		$post = get_post( get_post()->post_parent );
 	else
-		$post = get_adjacent_post( $in_same_cat, $excluded_categories, $previous );
+		$post = get_adjacent_post( $in_same_term, $excluded_terms, $previous, $taxonomy );
 
 	if ( ! $post ) {
 		$output = '';
@@ -1427,6 +1878,7 @@
 
 		/** This filter is documented in wp-includes/post-template.php */
 		$title = apply_filters( 'the_title', $title, $post->ID );
+
 		$date = mysql2date( get_option( 'date_format' ), $post->post_date );
 		$rel = $previous ? 'prev' : 'next';
 
@@ -1440,7 +1892,22 @@
 
 	$adjacent = $previous ? 'previous' : 'next';
 
-	return apply_filters( "{$adjacent}_post_link", $output, $format, $link, $post );
+	/**
+	 * Filter the adjacent post link.
+	 *
+	 * The dynamic portion of the hook name, `$adjacent`, refers to the type
+	 * of adjacency, 'next' or 'previous'.
+	 *
+	 * @since 2.6.0
+	 * @since 4.2.0 Added the `$adjacent` parameter.
+	 *
+	 * @param string  $output   The adjacent post link.
+	 * @param string  $format   Link anchor format.
+	 * @param string  $link     Link permalink format.
+	 * @param WP_Post $post     The adjacent post.
+	 * @param string  $adjacent Whether the post is previous or next.
+	 */
+	return apply_filters( "{$adjacent}_post_link", $output, $format, $link, $post, $adjacent );
 }
 
 /**
@@ -1449,17 +1916,16 @@
  * Can be either next post link or previous.
  *
  * @since 2.5.0
- * @uses get_adjacent_post_link()
  *
- * @param string $format Link anchor format.
- * @param string $link Link permalink format.
- * @param bool $in_same_cat Optional. Whether link should be in a same category.
- * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
- * @param bool $previous Optional, default is true. Whether to display link to previous or next post.
- * @return string
+ * @param string       $format         Link anchor format.
+ * @param string       $link           Link permalink format.
+ * @param bool         $in_same_term   Optional. Whether link should be in a same taxonomy term.
+ * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded category IDs.
+ * @param bool         $previous       Optional. Whether to display link to previous or next post. Default true.
+ * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
  */
-function adjacent_post_link( $format, $link, $in_same_cat = false, $excluded_categories = '', $previous = true ) {
-	echo get_adjacent_post_link( $format, $link, $in_same_cat, $excluded_categories, $previous );
+function adjacent_post_link( $format, $link, $in_same_term = false, $excluded_terms = '', $previous = true, $taxonomy = 'category' ) {
+	echo get_adjacent_post_link( $format, $link, $in_same_term, $excluded_terms, $previous, $taxonomy );
 }
 
 /**
@@ -1470,7 +1936,7 @@
  * @param int $pagenum Optional. Page ID.
  * @param bool $escape Optional. Whether to escape the URL for display, with esc_url(). Defaults to true.
 * 	Otherwise, prepares the URL with esc_url_raw().
- * @return string
+ * @return string The link URL for the given page number.
  */
 function get_pagenum_link($pagenum = 1, $escape = true ) {
 	global $wp_rewrite;
@@ -1521,7 +1987,14 @@
 		$result = $base . $request . $query_string;
 	}
 
-	$result = apply_filters('get_pagenum_link', $result);
+	/**
+	 * Filter the page number link for the current request.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param string $result The page number link.
+	 */
+	$result = apply_filters( 'get_pagenum_link', $result );
 
 	if ( $escape )
 		return esc_url( $result );
@@ -1537,7 +2010,7 @@
  * @since 2.0.10
  *
  * @param int $max_page Optional. Max pages.
- * @return string
+ * @return string The link URL for next posts page.
  */
 function get_next_posts_page_link($max_page = 0) {
 	global $paged;
@@ -1558,6 +2031,7 @@
  *
  * @param int $max_page Optional. Max pages.
  * @param boolean $echo Optional. Echo or return;
+ * @return string The link URL for next posts page if `$echo = false`.
  */
 function next_posts( $max_page = 0, $echo = true ) {
 	$output = esc_url( get_next_posts_page_link( $max_page ) );
@@ -1575,7 +2049,7 @@
  *
  * @param string $label Content for link text.
  * @param int $max_page Optional. Max pages.
- * @return string|null
+ * @return string|null HTML-formatted next posts page link.
  */
 function get_next_posts_link( $label = null, $max_page = 0 ) {
 	global $paged, $wp_query;
@@ -1592,7 +2066,15 @@
 		$label = __( 'Next Page &raquo;' );
 
 	if ( !is_single() && ( $nextpage <= $max_page ) ) {
+		/**
+		 * Filter the anchor tag attributes for the next posts page link.
+		 *
+		 * @since 2.7.0
+		 *
+		 * @param string $attributes Attributes for the anchor tag.
+		 */
 		$attr = apply_filters( 'next_posts_link_attributes', '' );
+
 		return '<a href="' . next_posts( $max_page, false ) . "\" $attr>" . preg_replace('/&([^#])(?![a-z]{1,8};)/i', '&#038;$1', $label) . '</a>';
 	}
 }
@@ -1601,7 +2083,6 @@
  * Display the next posts page link.
  *
  * @since 0.71
- * @uses get_next_posts_link()
  *
  * @param string $label Content for link text.
  * @param int $max_page Optional. Max pages.
@@ -1619,7 +2100,7 @@
  *
  * @since 2.0.10
  *
- * @return string|null
+ * @return string|null The link for the previous posts page.
  */
 function get_previous_posts_page_link() {
 	global $paged;
@@ -1638,6 +2119,7 @@
  * @since 0.71
  *
  * @param boolean $echo Optional. Echo or return;
+ * @return string The previous posts page link if `$echo = false`.
  */
 function previous_posts( $echo = true ) {
 	$output = esc_url( get_previous_posts_page_link() );
@@ -1654,7 +2136,7 @@
  * @since 2.7.0
  *
  * @param string $label Optional. Previous page link text.
- * @return string|null
+ * @return string|null HTML-formatted previous page link.
  */
 function get_previous_posts_link( $label = null ) {
 	global $paged;
@@ -1663,6 +2145,13 @@
 		$label = __( '&laquo; Previous Page' );
 
 	if ( !is_single() && $paged > 1 ) {
+		/**
+		 * Filter the anchor tag attributes for the previous posts page link.
+		 *
+		 * @since 2.7.0
+		 *
+		 * @param string $attributes Attributes for the anchor tag.
+		 */
 		$attr = apply_filters( 'previous_posts_link_attributes', '' );
 		return '<a href="' . previous_posts( false ) . "\" $attr>". preg_replace( '/&([^#])(?![a-z]{1,8};)/i', '&#038;$1', $label ) .'</a>';
 	}
@@ -1672,7 +2161,6 @@
  * Display the previous posts page link.
  *
  * @since 0.71
- * @uses get_previous_posts_link()
  *
  * @param string $label Optional. Previous page link text.
  */
@@ -1683,7 +2171,7 @@
 /**
  * Return post pages link navigation for previous and next pages.
  *
- * @since 2.8
+ * @since 2.8.0
  *
  * @param string|array $args Optional args.
  * @return string The posts link navigation.
@@ -1734,12 +2222,197 @@
 }
 
 /**
+ * Return navigation to next/previous post when applicable.
+ *
+ * @since 4.1.0
+ *
+ * @param array $args {
+ *     Optional. Default post navigation arguments. Default empty array.
+ *
+ *     @type string $prev_text          Anchor text to display in the previous post link. Default `%title`.
+ *     @type string $next_text          Anchor text to display in the next post link. Default `%title`.
+ *     @type string $screen_reader_text Screen reader text for nav element. Default 'Post navigation'.
+ * }
+ * @return string Markup for post links.
+ */
+function get_the_post_navigation( $args = array() ) {
+	$args = wp_parse_args( $args, array(
+		'prev_text'          => '%title',
+		'next_text'          => '%title',
+		'screen_reader_text' => __( 'Post navigation' ),
+	) );
+
+	$navigation = '';
+	$previous   = get_previous_post_link( '<div class="nav-previous">%link</div>', $args['prev_text'] );
+	$next       = get_next_post_link( '<div class="nav-next">%link</div>', $args['next_text'] );
+
+	// Only add markup if there's somewhere to navigate to.
+	if ( $previous || $next ) {
+		$navigation = _navigation_markup( $previous . $next, 'post-navigation', $args['screen_reader_text'] );
+	}
+
+	return $navigation;
+}
+
+/**
+ * Display navigation to next/previous post when applicable.
+ *
+ * @since 4.1.0
+ *
+ * @param array $args Optional. See {@see get_the_post_navigation()} for available
+ *                    arguments. Default empty array.
+ */
+function the_post_navigation( $args = array() ) {
+	echo get_the_post_navigation( $args );
+}
+
+/**
+ * Return navigation to next/previous set of posts when applicable.
+ *
+ * @since 4.1.0
+ *
+ * @global WP_Query $wp_query WordPress Query object.
+ *
+ * @param array $args {
+ *     Optional. Default posts navigation arguments. Default empty array.
+ *
+ *     @type string $prev_text          Anchor text to display in the previous posts link.
+ *                                      Default 'Older posts'.
+ *     @type string $next_text          Anchor text to display in the next posts link.
+ *                                      Default 'Newer posts'.
+ *     @type string $screen_reader_text Screen reader text for nav element.
+ *                                      Default 'Posts navigation'.
+ * }
+ * @return string Markup for posts links.
+ */
+function get_the_posts_navigation( $args = array() ) {
+	$navigation = '';
+
+	// Don't print empty markup if there's only one page.
+	if ( $GLOBALS['wp_query']->max_num_pages > 1 ) {
+		$args = wp_parse_args( $args, array(
+			'prev_text'          => __( 'Older posts' ),
+			'next_text'          => __( 'Newer posts' ),
+			'screen_reader_text' => __( 'Posts navigation' ),
+		) );
+
+		$next_link = get_previous_posts_link( $args['next_text'] );
+		$prev_link = get_next_posts_link( $args['prev_text'] );
+
+		if ( $prev_link ) {
+			$navigation .= '<div class="nav-previous">' . $prev_link . '</div>';
+		}
+
+		if ( $next_link ) {
+			$navigation .= '<div class="nav-next">' . $next_link . '</div>';
+		}
+
+		$navigation = _navigation_markup( $navigation, 'posts-navigation', $args['screen_reader_text'] );
+	}
+
+	return $navigation;
+}
+
+/**
+ * Display navigation to next/previous set of posts when applicable.
+ *
+ * @since 4.1.0
+ *
+ * @param array $args Optional. See {@see get_the_posts_navigation()} for available
+ *                    arguments. Default empty array.
+ */
+function the_posts_navigation( $args = array() ) {
+	echo get_the_posts_navigation( $args );
+}
+
+/**
+ * Return a paginated navigation to next/previous set of posts,
+ * when applicable.
+ *
+ * @since 4.1.0
+ *
+ * @param array $args {
+ *     Optional. Default pagination arguments, {@see paginate_links()}.
+ *
+ *     @type string $screen_reader_text Screen reader text for navigation element.
+ *                                      Default 'Posts navigation'.
+ * }
+ * @return string Markup for pagination links.
+ */
+function get_the_posts_pagination( $args = array() ) {
+	$navigation = '';
+
+	// Don't print empty markup if there's only one page.
+	if ( $GLOBALS['wp_query']->max_num_pages > 1 ) {
+		$args = wp_parse_args( $args, array(
+			'mid_size'           => 1,
+			'prev_text'          => _x( 'Previous', 'previous post' ),
+			'next_text'          => _x( 'Next', 'next post' ),
+			'screen_reader_text' => __( 'Posts navigation' ),
+		) );
+
+		// Make sure we get a string back. Plain is the next best thing.
+		if ( isset( $args['type'] ) && 'array' == $args['type'] ) {
+			$args['type'] = 'plain';
+		}
+
+		// Set up paginated links.
+		$links = paginate_links( $args );
+
+		if ( $links ) {
+			$navigation = _navigation_markup( $links, 'pagination', $args['screen_reader_text'] );
+		}
+	}
+
+	return $navigation;
+}
+
+/**
+ * Display a paginated navigation to next/previous set of posts,
+ * when applicable.
+ *
+ * @since 4.1.0
+ *
+ * @param array $args Optional. See {@see get_the_posts_pagination()} for available arguments.
+ *                    Default empty array.
+ */
+function the_posts_pagination( $args = array() ) {
+	echo get_the_posts_pagination( $args );
+}
+
+/**
+ * Wraps passed links in navigational markup.
+ *
+ * @since 4.1.0
+ * @access private
+ *
+ * @param string $links              Navigational links.
+ * @param string $class              Optional. Custom class for nav element. Default: 'posts-navigation'.
+ * @param string $screen_reader_text Optional. Screen reader text for nav element. Default: 'Posts navigation'.
+ * @return string Navigation template tag.
+ */
+function _navigation_markup( $links, $class = 'posts-navigation', $screen_reader_text = '' ) {
+	if ( empty( $screen_reader_text ) ) {
+		$screen_reader_text = __( 'Posts navigation' );
+	}
+
+	$template = '
+	<nav class="navigation %1$s" role="navigation">
+		<h2 class="screen-reader-text">%2$s</h2>
+		<div class="nav-links">%3$s</div>
+	</nav>';
+
+	return sprintf( $template, sanitize_html_class( $class ), esc_html( $screen_reader_text ), $links );
+}
+
+/**
  * Retrieve comments page number link.
  *
  * @since 2.7.0
  *
  * @param int $pagenum Optional. Page number.
- * @return string
+ * @param int $max_page Optional. The maximum number of comment pages.
+ * @return string The comments page number link URL.
  */
 function get_comments_pagenum_link( $pagenum = 1, $max_page = 0 ) {
 	global $wp_rewrite;
@@ -1751,20 +2424,27 @@
 	if ( 'newest' == get_option('default_comments_page') ) {
 		if ( $pagenum != $max_page ) {
 			if ( $wp_rewrite->using_permalinks() )
-				$result = user_trailingslashit( trailingslashit($result) . 'comment-page-' . $pagenum, 'commentpaged');
+				$result = user_trailingslashit( trailingslashit($result) . $wp_rewrite->comments_pagination_base . '-' . $pagenum, 'commentpaged');
 			else
 				$result = add_query_arg( 'cpage', $pagenum, $result );
 		}
 	} elseif ( $pagenum > 1 ) {
 		if ( $wp_rewrite->using_permalinks() )
-			$result = user_trailingslashit( trailingslashit($result) . 'comment-page-' . $pagenum, 'commentpaged');
+			$result = user_trailingslashit( trailingslashit($result) . $wp_rewrite->comments_pagination_base . '-' . $pagenum, 'commentpaged');
 		else
 			$result = add_query_arg( 'cpage', $pagenum, $result );
 	}
 
 	$result .= '#comments';
 
-	$result = apply_filters('get_comments_pagenum_link', $result);
+	/**
+	 * Filter the comments page number link for the current request.
+	 *
+	 * @since 2.7.0
+	 *
+	 * @param string $result The comments page number link.
+	 */
+	$result = apply_filters( 'get_comments_pagenum_link', $result );
 
 	return $result;
 }
@@ -1776,7 +2456,7 @@
  *
  * @param string $label Optional. Label for link text.
  * @param int $max_page Optional. Max page.
- * @return string|null
+ * @return string|null HTML-formatted link for the next page of comments.
  */
 function get_next_comments_link( $label = '', $max_page = 0 ) {
 	global $wp_query;
@@ -1786,6 +2466,10 @@
 
 	$page = get_query_var('cpage');
 
+	if ( ! $page ) {
+		$page = 1;
+	}
+
 	$nextpage = intval($page) + 1;
 
 	if ( empty($max_page) )
@@ -1800,6 +2484,13 @@
 	if ( empty($label) )
 		$label = __('Newer Comments &raquo;');
 
+	/**
+	 * Filter the anchor tag attributes for the next comments page link.
+	 *
+	 * @since 2.7.0
+	 *
+	 * @param string $attributes Attributes for the anchor tag.
+	 */
 	return '<a href="' . esc_url( get_comments_pagenum_link( $nextpage, $max_page ) ) . '" ' . apply_filters( 'next_comments_link_attributes', '' ) . '>'. preg_replace('/&([^#])(?![a-z]{1,8};)/i', '&#038;$1', $label) .'</a>';
 }
 
@@ -1821,7 +2512,7 @@
  * @since 2.7.1
  *
  * @param string $label Optional. Label for comments link text.
- * @return string|null
+ * @return string|null HTML-formatted link for the previous page of comments.
  */
 function get_previous_comments_link( $label = '' ) {
 	if ( !is_singular() || !get_option('page_comments') )
@@ -1837,6 +2528,13 @@
 	if ( empty($label) )
 		$label = __('&laquo; Older Comments');
 
+	/**
+	 * Filter the anchor tag attributes for the previous comments page link.
+	 *
+	 * @since 2.7.0
+	 *
+	 * @param string $attributes Attributes for the anchor tag.
+	 */
 	return '<a href="' . esc_url( get_comments_pagenum_link( $prevpage ) ) . '" ' . apply_filters( 'previous_comments_link_attributes', '' ) . '>' . preg_replace('/&([^#])(?![a-z]{1,8};)/i', '&#038;$1', $label) .'</a>';
 }
 
@@ -1879,7 +2577,7 @@
 		'add_fragment' => '#comments'
 	);
 	if ( $wp_rewrite->using_permalinks() )
-		$defaults['base'] = user_trailingslashit(trailingslashit(get_permalink()) . 'comment-page-%#%', 'commentpaged');
+		$defaults['base'] = user_trailingslashit(trailingslashit(get_permalink()) . $wp_rewrite->comments_pagination_base . '-%#%', 'commentpaged');
 
 	$args = wp_parse_args( $args, $defaults );
 	$page_links = paginate_links( $args );
@@ -1897,44 +2595,69 @@
  *
  * @since 2.6.0
  *
- * @return string
+ * @return string The Press This bookmarklet link URL.
  */
 function get_shortcut_link() {
-	// In case of breaking changes, version this. #WP20071
-	$link = "javascript:
-			var d=document,
-			w=window,
-			e=w.getSelection,
-			k=d.getSelection,
-			x=d.selection,
-			s=(e?e():(k)?k():(x?x.createRange().text:0)),
-			f='" . admin_url('press-this.php') . "',
-			l=d.location,
-			e=encodeURIComponent,
-			u=f+'?u='+e(l.href)+'&t='+e(d.title)+'&s='+e(s)+'&v=4';
-			a=function(){if(!w.open(u,'t','toolbar=0,resizable=1,scrollbars=1,status=1,width=720,height=570'))l.href=u;};
-			if (/Firefox/.test(navigator.userAgent)) setTimeout(a, 0); else a();
-			void(0)";
-
-	$link = str_replace(array("\r", "\n", "\t"),  '', $link);
-
-	return apply_filters('shortcut_link', $link);
+	global $is_IE, $wp_version;
+
+	include_once( ABSPATH . 'wp-admin/includes/class-wp-press-this.php' );
+	$bookmarklet_version = $GLOBALS['wp_press_this']->version;
+	$link = '';
+
+	if ( $is_IE ) {
+		/**
+		 * Return the old/shorter bookmarklet code for MSIE 8 and lower,
+		 * since they only support a max length of ~2000 characters for
+		 * bookmark[let] URLs, which is way to small for our smarter one.
+		 * Do update the version number so users do not get the "upgrade your
+		 * bookmarklet" notice when using PT in those browsers.
+		 */
+		$ua = $_SERVER['HTTP_USER_AGENT'];
+
+		if ( ! empty( $ua ) && preg_match( '/\bMSIE (\d)/', $ua, $matches ) && (int) $matches[1] <= 8 ) {
+			$url = wp_json_encode( admin_url( 'press-this.php' ) );
+
+			$link = 'javascript:var d=document,w=window,e=w.getSelection,k=d.getSelection,x=d.selection,' .
+				's=(e?e():(k)?k():(x?x.createRange().text:0)),f=' . $url . ',l=d.location,e=encodeURIComponent,' .
+				'u=f+"?u="+e(l.href)+"&t="+e(d.title)+"&s="+e(s)+"&v=' . $bookmarklet_version . '";' .
+				'a=function(){if(!w.open(u,"t","toolbar=0,resizable=1,scrollbars=1,status=1,width=600,height=700"))l.href=u;};' .
+				'if(/Firefox/.test(navigator.userAgent))setTimeout(a,0);else a();void(0)';
+		}
+	}
+
+	if ( empty( $link ) ) {
+		$src = @file_get_contents( ABSPATH . 'wp-admin/js/bookmarklet.min.js' );
+
+		if ( $src ) {
+			$url = wp_json_encode( admin_url( 'press-this.php' ) . '?v=' . $bookmarklet_version );
+			$link = 'javascript:' . str_replace( 'window.pt_url', $url, $src );
+		}
+	}
+
+	$link = str_replace( array( "\r", "\n", "\t" ),  '', $link );
+
+	/**
+	 * Filter the Press This bookmarklet link.
+	 *
+	 * @since 2.6.0
+	 *
+	 * @param string $link The Press This bookmarklet link.
+	 */
+	return apply_filters( 'shortcut_link', $link );
 }
 
 /**
  * Retrieve the home url for the current site.
  *
  * Returns the 'home' option with the appropriate protocol, 'https' if
- * is_ssl() and 'http' otherwise. If $scheme is 'http' or 'https', is_ssl() is
- * overridden.
+ * {@see is_ssl()} and 'http' otherwise. If `$scheme` is 'http' or 'https',
+ * `is_ssl()` is overridden.
  *
- * @package WordPress
  * @since 3.0.0
  *
- * @uses get_home_url()
- *
- * @param  string $path   (optional) Path relative to the home url.
- * @param  string $scheme (optional) Scheme to give the home url context. Currently 'http', 'https', or 'relative'.
+ * @param  string $path   Optional. Path relative to the home url. Default empty.
+ * @param  string $scheme Optional. Scheme to give the home url context. Accepts
+ *                        'http', 'https', or 'relative'. Default null.
  * @return string Home url link with optional path appended.
 */
 function home_url( $path = '', $scheme = null ) {
@@ -1945,16 +2668,17 @@
  * Retrieve the home url for a given site.
  *
  * Returns the 'home' option with the appropriate protocol, 'https' if
- * is_ssl() and 'http' otherwise. If $scheme is 'http' or 'https', is_ssl() is
+ * {@see is_ssl()} and 'http' otherwise. If `$scheme` is 'http' or 'https',
+ * `is_ssl()` is
  * overridden.
  *
- * @package WordPress
  * @since 3.0.0
  *
- * @param  int $blog_id   (optional) Blog ID. Defaults to current blog.
- * @param  string $path   (optional) Path relative to the home url.
- * @param  string $scheme (optional) Scheme to give the home url context. Currently 'http', 'https', or 'relative'.
- * @return string Home url link with optional path appended.
+ * @param  int         $blog_id     Optional. Blog ID. Default null (current blog).
+ * @param  string      $path        Optional. Path relative to the home URL. Default empty.
+ * @param  string|null $orig_scheme Optional. Scheme to give the home URL context. Accepts
+ *                                  'http', 'https', 'relative', or null. Default null.
+ * @return string Home URL link with optional path appended.
 */
 function get_home_url( $blog_id = null, $path = '', $scheme = null ) {
 	$orig_scheme = $scheme;
@@ -1979,6 +2703,16 @@
 	if ( $path && is_string( $path ) )
 		$url .= '/' . ltrim( $path, '/' );
 
+	/**
+	 * Filter the home URL.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param string      $url         The complete home URL including scheme and path.
+	 * @param string      $path        Path relative to the home URL. Blank string if no path is specified.
+	 * @param string|null $orig_scheme Scheme to give the home URL context. Accepts 'http', 'https', 'relative' or null.
+	 * @param int|null    $blog_id     Blog ID, or null for the current blog.
+	 */
 	return apply_filters( 'home_url', $url, $path, $orig_scheme, $blog_id );
 }
 
@@ -1989,10 +2723,7 @@
  * is_ssl() and 'http' otherwise. If $scheme is 'http' or 'https', is_ssl() is
  * overridden.
  *
- * @package WordPress
- * @since 2.6.0
- *
- * @uses get_site_url()
+ * @since 3.0.0
  *
  * @param string $path Optional. Path relative to the site url.
  * @param string $scheme Optional. Scheme to give the site url context. See set_url_scheme().
@@ -2006,15 +2737,16 @@
  * Retrieve the site url for a given site.
  *
  * Returns the 'site_url' option with the appropriate protocol, 'https' if
- * is_ssl() and 'http' otherwise. If $scheme is 'http' or 'https', is_ssl() is
- * overridden.
+ * {@see is_ssl()} and 'http' otherwise. If `$scheme` is 'http' or 'https',
+ * `is_ssl()` is overridden.
  *
- * @package WordPress
  * @since 3.0.0
  *
- * @param int $blog_id (optional) Blog ID. Defaults to current blog.
- * @param string $path Optional. Path relative to the site url.
- * @param string $scheme Optional. Scheme to give the site url context. Currently 'http', 'https', 'login', 'login_post', 'admin', or 'relative'.
+ * @param int    $blog_id Optional. Blog ID. Default null (current site).
+ * @param string $path    Optional. Path relative to the site url. Default empty.
+ * @param string $scheme  Optional. Scheme to give the site url context. Accepts
+ *                        'http', 'https', 'login', 'login_post', 'admin', or
+ *                        'relative'. Default null.
  * @return string Site url link with optional path appended.
 */
 function get_site_url( $blog_id = null, $path = '', $scheme = null ) {
@@ -2031,13 +2763,23 @@
 	if ( $path && is_string( $path ) )
 		$url .= '/' . ltrim( $path, '/' );
 
+	/**
+	 * Filter the site URL.
+	 *
+	 * @since 2.7.0
+	 *
+	 * @param string      $url     The complete site URL including scheme and path.
+	 * @param string      $path    Path relative to the site URL. Blank string if no path is specified.
+	 * @param string|null $scheme  Scheme to give the site URL context. Accepts 'http', 'https', 'login',
+	 *                             'login_post', 'admin', 'relative' or null.
+	 * @param int|null    $blog_id Blog ID, or null for the current blog.
+	 */
 	return apply_filters( 'site_url', $url, $path, $scheme, $blog_id );
 }
 
 /**
  * Retrieve the url to the admin area for the current site.
  *
- * @package WordPress
  * @since 2.6.0
  *
  * @param string $path Optional path relative to the admin url.
@@ -2049,14 +2791,15 @@
 }
 
 /**
- * Retrieve the url to the admin area for a given site.
+ * Retrieves the url to the admin area for a given site.
  *
- * @package WordPress
  * @since 3.0.0
  *
- * @param int $blog_id (optional) Blog ID. Defaults to current blog.
- * @param string $path Optional path relative to the admin url.
- * @param string $scheme The scheme to use. Default is 'admin', which obeys force_ssl_admin() and is_ssl(). 'http' or 'https' can be passed to force those schemes.
+ * @param int    $blog_id Optional. Blog ID. Default null (current site).
+ * @param string $path    Optional. Path relative to the admin url. Default empty.
+ * @param string $scheme  Optional. The scheme to use. Accepts 'http' or 'https',
+ *                        to force those schemes. Default 'admin', which obeys
+ *                        {@see force_ssl_admin()} and {@see is_ssl()}.
  * @return string Admin url link with optional path appended.
 */
 function get_admin_url( $blog_id = null, $path = '', $scheme = 'admin' ) {
@@ -2065,13 +2808,21 @@
 	if ( $path && is_string( $path ) )
 		$url .= ltrim( $path, '/' );
 
+	/**
+	 * Filter the admin area URL.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @param string   $url     The complete admin area URL including scheme and path.
+	 * @param string   $path    Path relative to the admin area URL. Blank string if no path is specified.
+	 * @param int|null $blog_id Blog ID, or null for the current blog.
+	 */
 	return apply_filters( 'admin_url', $url, $path, $blog_id );
 }
 
 /**
  * Retrieve the url to the includes directory.
  *
- * @package WordPress
  * @since 2.6.0
  *
  * @param string $path Optional. Path relative to the includes url.
@@ -2084,13 +2835,21 @@
 	if ( $path && is_string( $path ) )
 		$url .= ltrim($path, '/');
 
-	return apply_filters('includes_url', $url, $path);
+	/**
+	 * Filter the URL to the includes directory.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @param string $url  The complete URL to the includes directory including scheme and path.
+	 * @param string $path Path relative to the URL to the wp-includes directory. Blank string
+	 *                     if no path is specified.
+	 */
+	return apply_filters( 'includes_url', $url, $path );
 }
 
 /**
  * Retrieve the url to the content directory.
  *
- * @package WordPress
  * @since 2.6.0
  *
  * @param string $path Optional. Path relative to the content url.
@@ -2102,27 +2861,37 @@
 	if ( $path && is_string( $path ) )
 		$url .= '/' . ltrim($path, '/');
 
-	return apply_filters('content_url', $url, $path);
+	/**
+	 * Filter the URL to the content directory.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @param string $url  The complete URL to the content directory including scheme and path.
+	 * @param string $path Path relative to the URL to the content directory. Blank string
+	 *                     if no path is specified.
+	 */
+	return apply_filters( 'content_url', $url, $path);
 }
 
 /**
- * Retrieve the url to the plugins directory or to a specific file within that directory.
- * You can hardcode the plugin slug in $path or pass __FILE__ as a second argument to get the correct folder name.
+ * Retrieve a URL within the plugins or mu-plugins directory.
  *
- * @package WordPress
+ * Defaults to the plugins directory URL if no arguments are supplied.
+ *
  * @since 2.6.0
  *
- * @param string $path Optional. Path relative to the plugins url.
- * @param string $plugin Optional. The plugin file that you want to be relative to - i.e. pass in __FILE__
- * @return string Plugins url link with optional path appended.
+ * @param  string $path   Optional. Extra path appended to the end of the URL, including
+ *                        the relative directory if $plugin is supplied. Default empty.
+ * @param  string $plugin Optional. A full path to a file inside a plugin or mu-plugin.
+ *                        The URL will be relative to its directory. Default empty.
+ *                        Typically this is done by passing `__FILE__` as the argument.
+ * @return string Plugins URL link with optional paths appended.
 */
-function plugins_url($path = '', $plugin = '') {
-
-	$mu_plugin_dir = WPMU_PLUGIN_DIR;
-	foreach ( array('path', 'plugin', 'mu_plugin_dir') as $var ) {
-		$$var = str_replace('\\' ,'/', $$var); // sanitize for Win32 installs
-		$$var = preg_replace('|/+|', '/', $$var);
-	}
+function plugins_url( $path = '', $plugin = '' ) {
+
+	$path = wp_normalize_path( $path );
+	$plugin = wp_normalize_path( $plugin );
+	$mu_plugin_dir = wp_normalize_path( WPMU_PLUGIN_DIR );
 
 	if ( !empty($plugin) && 0 === strpos($plugin, $mu_plugin_dir) )
 		$url = WPMU_PLUGIN_URL;
@@ -2141,7 +2910,18 @@
 	if ( $path && is_string( $path ) )
 		$url .= '/' . ltrim($path, '/');
 
-	return apply_filters('plugins_url', $url, $path, $plugin);
+	/**
+	 * Filter the URL to the plugins directory.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @param string $url    The complete URL to the plugins directory including scheme and path.
+	 * @param string $path   Path relative to the URL to the plugins directory. Blank string
+	 *                       if no path is specified.
+	 * @param string $plugin The plugin file path to be relative to. Blank string if no plugin
+	 *                       is specified.
+	 */
+	return apply_filters( 'plugins_url', $url, $path, $plugin );
 }
 
 /**
@@ -2151,7 +2931,6 @@
  * is_ssl() and 'http' otherwise. If $scheme is 'http' or 'https', is_ssl() is
  * overridden.
  *
- * @package WordPress
  * @since 3.0.0
  *
  * @param string $path Optional. Path relative to the site url.
@@ -2159,11 +2938,11 @@
  * @return string Site url link with optional path appended.
 */
 function network_site_url( $path = '', $scheme = null ) {
-	global $current_site;
-
 	if ( ! is_multisite() )
 		return site_url($path, $scheme);
 
+	$current_site = get_current_site();
+
 	if ( 'relative' == $scheme )
 		$url = $current_site->path;
 	else
@@ -2172,29 +2951,39 @@
 	if ( $path && is_string( $path ) )
 		$url .= ltrim( $path, '/' );
 
+	/**
+	 * Filter the network site URL.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param string      $url    The complete network site URL including scheme and path.
+	 * @param string      $path   Path relative to the network site URL. Blank string if
+	 *                            no path is specified.
+	 * @param string|null $scheme Scheme to give the URL context. Accepts 'http', 'https',
+	 *                            'relative' or null.
+	 */
 	return apply_filters( 'network_site_url', $url, $path, $scheme );
 }
 
 /**
- * Retrieve the home url for the current network.
+ * Retrieves the home url for the current network.
  *
- * Returns the home url with the appropriate protocol, 'https' if
- * is_ssl() and 'http' otherwise. If $scheme is 'http' or 'https', is_ssl() is
+ * Returns the home url with the appropriate protocol, 'https' {@see is_ssl()}
+ * and 'http' otherwise. If `$scheme` is 'http' or 'https', `is_ssl()` is
  * overridden.
  *
- * @package WordPress
  * @since 3.0.0
  *
- * @param  string $path   (optional) Path relative to the home url.
- * @param  string $scheme (optional) Scheme to give the home url context. Currently 'http', 'https', or 'relative'.
+ * @param  string $path   Optional. Path relative to the home url. Default empty.
+ * @param  string $scheme Optional. Scheme to give the home url context. Accepts
+ *                        'http', 'https', or 'relative'. Default null.
  * @return string Home url link with optional path appended.
 */
 function network_home_url( $path = '', $scheme = null ) {
-	global $current_site;
-
 	if ( ! is_multisite() )
 		return home_url($path, $scheme);
 
+	$current_site = get_current_site();
 	$orig_scheme = $scheme;
 
 	if ( ! in_array( $scheme, array( 'http', 'https', 'relative' ) ) )
@@ -2208,13 +2997,23 @@
 	if ( $path && is_string( $path ) )
 		$url .= ltrim( $path, '/' );
 
+	/**
+	 * Filter the network home URL.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param string      $url         The complete network home URL including scheme and path.
+	 * @param string      $path        Path relative to the network home URL. Blank string
+	 *                                 if no path is specified.
+	 * @param string|null $orig_scheme Scheme to give the URL context. Accepts 'http', 'https',
+	 *                                 'relative' or null.
+	 */
 	return apply_filters( 'network_home_url', $url, $path, $orig_scheme);
 }
 
 /**
  * Retrieve the url to the admin area for the network.
  *
- * @package WordPress
  * @since 3.0.0
  *
  * @param string $path Optional path relative to the admin url.
@@ -2230,13 +3029,21 @@
 	if ( $path && is_string( $path ) )
 		$url .= ltrim($path, '/');
 
-	return apply_filters('network_admin_url', $url, $path);
+	/**
+	 * Filter the network admin URL.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param string $url  The complete network admin URL including scheme and path.
+	 * @param string $path Path relative to the network admin URL. Blank string if
+	 *                     no path is specified.
+	 */
+	return apply_filters( 'network_admin_url', $url, $path );
 }
 
 /**
  * Retrieve the url to the admin area for the current user.
  *
- * @package WordPress
  * @since 3.0.0
  *
  * @param string $path Optional path relative to the admin url.
@@ -2249,13 +3056,21 @@
 	if ( $path && is_string( $path ) )
 		$url .= ltrim($path, '/');
 
-	return apply_filters('user_admin_url', $url, $path);
+	/**
+	 * Filter the user admin URL for the current user.
+	 *
+	 * @since 3.1.0
+	 *
+	 * @param string $url  The complete URL including scheme and path.
+	 * @param string $path Path relative to the URL. Blank string if
+	 *                     no path is specified.
+	 */
+	return apply_filters( 'user_admin_url', $url, $path );
 }
 
 /**
  * Retrieve the url to the admin area for either the current blog or the network depending on context.
  *
- * @package WordPress
  * @since 3.1.0
  *
  * @param string $path Optional path relative to the admin url.
@@ -2282,15 +3097,13 @@
  */
 function set_url_scheme( $url, $scheme = null ) {
 	$orig_scheme = $scheme;
-	if ( ! in_array( $scheme, array( 'http', 'https', 'relative' ) ) ) {
-		if ( ( 'login_post' == $scheme || 'rpc' == $scheme ) && ( force_ssl_login() || force_ssl_admin() ) )
-			$scheme = 'https';
-		elseif ( ( 'login' == $scheme ) && force_ssl_admin() )
-			$scheme = 'https';
-		elseif ( ( 'admin' == $scheme ) && force_ssl_admin() )
-			$scheme = 'https';
-		else
-			$scheme = ( is_ssl() ? 'https' : 'http' );
+
+	if ( ! $scheme ) {
+		$scheme = is_ssl() ? 'https' : 'http';
+	} elseif ( $scheme === 'admin' || $scheme === 'login' || $scheme === 'login_post' || $scheme === 'rpc' ) {
+		$scheme = is_ssl() || force_ssl_admin() ? 'https' : 'http';
+	} elseif ( $scheme !== 'http' && $scheme !== 'https' && $scheme !== 'relative' ) {
+		$scheme = is_ssl() ? 'https' : 'http';
 	}
 
 	$url = trim( $url );
@@ -2305,6 +3118,16 @@
 		$url = preg_replace( '#^\w+://#', $scheme . '://', $url );
 	}
 
+	/**
+	 * Filter the resulting URL after setting the scheme.
+	 *
+	 * @since 3.4.0
+	 *
+	 * @param string $url         The complete URL including scheme and path.
+	 * @param string $scheme      Scheme applied to the URL. One of 'http', 'https', or 'relative'.
+	 * @param string $orig_scheme Scheme requested for the URL. One of 'http', 'https', 'login',
+	 *                            'login_post', 'admin', 'rpc', or 'relative'.
+	 */
 	return apply_filters( 'set_url_scheme', $url, $scheme, $orig_scheme );
 }
 
@@ -2317,13 +3140,13 @@
  *
  * @since 3.1.0
  *
- * @param int $user_id User ID
+ * @param int $user_id Optional. User ID. Defaults to current user.
  * @param string $path Optional path relative to the dashboard. Use only paths known to both blog and user admins.
  * @param string $scheme The scheme to use. Default is 'admin', which obeys force_ssl_admin() and is_ssl(). 'http' or 'https' can be passed to force those schemes.
  * @return string Dashboard url link with optional path appended.
  */
-function get_dashboard_url( $user_id, $path = '', $scheme = 'admin' ) {
-	$user_id = (int) $user_id;
+function get_dashboard_url( $user_id = 0, $path = '', $scheme = 'admin' ) {
+	$user_id = $user_id ? (int) $user_id : get_current_user_id();
 
 	$blogs = get_blogs_of_user( $user_id );
 	if ( ! is_super_admin() && empty($blogs) ) {
@@ -2343,6 +3166,17 @@
 		}
 	}
 
+	/**
+	 * Filter the dashboard URL for a user.
+	 *
+	 * @since 3.1.0
+	 *
+	 * @param string $url     The complete URL including scheme and path.
+	 * @param int    $user_id The user ID.
+	 * @param string $path    Path relative to the URL. Blank string if no path is specified.
+	 * @param string $scheme  Scheme to give the URL context. Accepts 'http', 'https', 'login',
+	 *                        'login_post', 'admin', 'relative' or null.
+	 */
 	return apply_filters( 'user_dashboard_url', $url, $user_id, $path, $scheme);
 }
 
@@ -2351,27 +3185,37 @@
  *
  * @since 3.1.0
  *
- * @param int $user User ID
- * @param string $scheme The scheme to use. Default is 'admin', which obeys force_ssl_admin() and is_ssl(). 'http' or 'https' can be passed to force those schemes.
+ * @param int    $user_id Optional. User ID. Defaults to current user.
+ * @param string $scheme  The scheme to use. Default is 'admin', which obeys force_ssl_admin() and is_ssl().
+ *                        'http' or 'https' can be passed to force those schemes.
  * @return string Dashboard url link with optional path appended.
  */
-function get_edit_profile_url( $user, $scheme = 'admin' ) {
-	$user = (int) $user;
+function get_edit_profile_url( $user_id = 0, $scheme = 'admin' ) {
+	$user_id = $user_id ? (int) $user_id : get_current_user_id();
 
 	if ( is_user_admin() )
 		$url = user_admin_url( 'profile.php', $scheme );
 	elseif ( is_network_admin() )
 		$url = network_admin_url( 'profile.php', $scheme );
 	else
-		$url = get_dashboard_url( $user, 'profile.php', $scheme );
-
-	return apply_filters( 'edit_profile_url', $url, $user, $scheme);
+		$url = get_dashboard_url( $user_id, 'profile.php', $scheme );
+
+	/**
+	 * Filter the URL for a user's profile editor.
+	 *
+	 * @since 3.1.0
+	 *
+	 * @param string $url     The complete URL including scheme and path.
+	 * @param int    $user_id The user ID.
+	 * @param string $scheme  Scheme to give the URL context. Accepts 'http', 'https', 'login',
+	 *                        'login_post', 'admin', 'relative' or null.
+	 */
+	return apply_filters( 'edit_profile_url', $url, $user_id, $scheme);
 }
 
 /**
  * Output rel=canonical for singular queries.
  *
- * @package WordPress
  * @since 2.9.0
 */
 function rel_canonical() {
@@ -2406,8 +3250,21 @@
  * @return string A shortlink or an empty string if no shortlink exists for the requested resource or if shortlinks are not enabled.
  */
 function wp_get_shortlink($id = 0, $context = 'post', $allow_slugs = true) {
-	// Allow plugins to short-circuit this function.
-	$shortlink = apply_filters('pre_get_shortlink', false, $id, $context, $allow_slugs);
+	/**
+	 * Filter whether to preempt generating a shortlink for the given post.
+	 *
+	 * Passing a truthy value to the filter will effectively short-circuit the
+	 * shortlink-generation process, returning that value instead.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param bool|string $return      Short-circuit return value. Either false or a URL string.
+	 * @param int         $id          Post ID, or 0 for the current post.
+	 * @param string      $context     The context for the link. One of 'post' or 'query',
+	 * @param bool        $allow_slugs Whether to allow post slugs in the shortlink.
+	 */
+	$shortlink = apply_filters( 'pre_get_shortlink', false, $id, $context, $allow_slugs );
+
 	if ( false !== $shortlink )
 		return $shortlink;
 
@@ -2427,11 +3284,25 @@
 	// Return p= link for all public post types.
 	if ( ! empty( $post_id ) ) {
 		$post_type = get_post_type_object( $post->post_type );
-		if ( $post_type->public )
-			$shortlink = home_url('?p=' . $post_id);
+
+		if ( 'page' === $post->post_type && $post->ID == get_option( 'page_on_front' ) && 'page' == get_option( 'show_on_front' ) ) {
+			$shortlink = home_url( '/' );
+		} elseif ( $post_type->public ) {
+			$shortlink = home_url( '?p=' . $post_id );
+		}
 	}
 
-	return apply_filters('get_shortlink', $shortlink, $id, $context, $allow_slugs);
+	/**
+	 * Filter the shortlink for a post.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param string $shortlink   Shortlink URL.
+	 * @param int    $id          Post ID, or 0 for the current post.
+	 * @param string $context     The context for the link. One of 'post' or 'query',
+	 * @param bool   $allow_slugs Whether to allow post slugs in the shortlink. Not used by default.
+	 */
+	return apply_filters( 'get_shortlink', $shortlink, $id, $context, $allow_slugs );
 }
 
 /**
@@ -2440,8 +3311,6 @@
  *  Attached to the wp_head action.
  *
  * @since 3.0.0
- *
- * @uses wp_get_shortlink()
  */
 function wp_shortlink_wp_head() {
 	$shortlink = wp_get_shortlink( 0, 'query' );
@@ -2458,8 +3327,6 @@
  * Attached to the wp action.
  *
  * @since 3.0.0
- *
- * @uses wp_get_shortlink()
  */
 function wp_shortlink_header() {
 	if ( headers_sent() )
@@ -2500,7 +3367,265 @@
 
 	if ( !empty( $shortlink ) ) {
 		$link = '<a rel="shortlink" href="' . esc_url( $shortlink ) . '" title="' . $title . '">' . $text . '</a>';
+
+		/**
+		 * Filter the shortlink anchor tag for a post.
+		 *
+		 * @since 3.0.0
+		 *
+		 * @param string $link      Shortlink anchor tag.
+		 * @param string $shortlink Shortlink URL.
+		 * @param string $text      Shortlink's text.
+		 * @param string $title     Shortlink's title attribute.
+		 */
 		$link = apply_filters( 'the_shortlink', $link, $shortlink, $text, $title );
 		echo $before, $link, $after;
 	}
 }
+
+
+/**
+ * Retrieve the avatar URL.
+ *
+ * @since 4.2.0
+ *
+ * @param mixed $id_or_email The Gravatar to retrieve a URL for. Accepts a user_id, gravatar md5 hash,
+ *                           user email, WP_User object, WP_Post object, or comment object.
+ * @param array $args {
+ *     Optional. Arguments to return instead of the default arguments.
+ *
+ *     @type int    $size           Height and width of the avatar in pixels. Default 96.
+ *     @type string $default        URL for the default image or a default type. Accepts '404' (return
+ *                                  a 404 instead of a default image), 'retro' (8bit), 'monsterid' (monster),
+ *                                  'wavatar' (cartoon face), 'indenticon' (the "quilt"), 'mystery', 'mm',
+ *                                  or 'mysterman' (The Oyster Man), 'blank' (transparent GIF), or
+ *                                  'gravatar_default' (the Gravatar logo). Default is the value of the
+ *                                  'avatar_default' option, with a fallback of 'mystery'.
+ *     @type bool   $force_default  Whether to always show the default image, never the Gravatar. Default false.
+ *     @type string $rating         What rating to display avatars up to. Accepts 'G', 'PG', 'R', 'X', and are
+ *                                  judged in that order. Default is the value of the 'avatar_rating' option.
+ *     @type string $scheme         URL scheme to use. See set_url_scheme() for accepted values.
+ *                                  Default null.
+ *     @type array  $processed_args When the function returns, the value will be the processed/sanitized $args
+ *                                  plus a "found_avatar" guess. Pass as a reference. Default null.
+ * }
+ * @return false|string The URL of the avatar we found, or false if we couldn't find an avatar.
+ */
+function get_avatar_url( $id_or_email, $args = null ) {
+	$args = get_avatar_data( $id_or_email, $args );
+	return $args['url'];
+}
+
+/**
+ * Retrieve default data about the avatar.
+ *
+ * @since 4.2.0
+ *
+ * @param mixed $id_or_email The Gravatar to check the data against. Accepts a user_id, gravatar md5 hash,
+ *                           user email, WP_User object, WP_Post object, or comment object.
+ * @param array $args {
+ *     Optional. Arguments to return instead of the default arguments.
+ *
+ *     @type int    $size           Height and width of the avatar image file in pixels. Default 96.
+ *     @type int    $height         Display height of the avatar in pixels. Defaults to $size.
+ *     @type int    $width          Display width of the avatar in pixels. Defaults to $size.
+ *     @type string $default        URL for the default image or a default type. Accepts '404' (return
+ *                                  a 404 instead of a default image), 'retro' (8bit), 'monsterid' (monster),
+ *                                  'wavatar' (cartoon face), 'indenticon' (the "quilt"), 'mystery', 'mm',
+ *                                  or 'mysterman' (The Oyster Man), 'blank' (transparent GIF), or
+ *                                  'gravatar_default' (the Gravatar logo). Default is the value of the
+ *                                  'avatar_default' option, with a fallback of 'mystery'.
+ *     @type bool   $force_default  Whether to always show the default image, never the Gravatar. Default false.
+ *     @type string $rating         What rating to display avatars up to. Accepts 'G', 'PG', 'R', 'X', and are
+ *                                  judged in that order. Default is the value of the 'avatar_rating' option.
+ *     @type string $scheme         URL scheme to use. See set_url_scheme() for accepted values.
+ *                                  Default null.
+ *     @type array  $processed_args When the function returns, the value will be the processed/sanitized $args
+ *                                  plus a "found_avatar" guess. Pass as a reference. Default null.
+ *     @type string $extra_attr     HTML attributes to insert in the IMG element. Is not sanitized. Default empty.
+ * }
+ * @return array $processed_args {
+ *     Along with the arguments passed in `$args`, this will contain a couple of extra arguments.
+ *
+ *     @type bool   $found_avatar True if we were able to find an avatar for this user,
+ *                                false or not set if we couldn't.
+ *     @type string $url          The URL of the avatar we found.
+ * }
+ */
+function get_avatar_data( $id_or_email, $args = null ) {
+	$args = wp_parse_args( $args, array(
+		'size'           => 96,
+		'height'         => null,
+		'width'          => null,
+		'default'        => get_option( 'avatar_default', 'mystery' ),
+		'force_default'  => false,
+		'rating'         => get_option( 'avatar_rating' ),
+		'scheme'         => null,
+		'processed_args' => null, // if used, should be a reference
+		'extra_attr'     => '',
+	) );
+
+	if ( is_numeric( $args['size'] ) ) {
+		$args['size'] = absint( $args['size'] );
+		if ( ! $args['size'] ) {
+			$args['size'] = 96;
+		}
+	} else {
+		$args['size'] = 96;
+	}
+
+	if ( is_numeric( $args['height'] ) ) {
+		$args['height'] = absint( $args['height'] );
+		if ( ! $args['height'] ) {
+			$args['height'] = $args['size'];
+		}
+	} else {
+		$args['height'] = $args['size'];
+	}
+
+	if ( is_numeric( $args['width'] ) ) {
+		$args['width'] = absint( $args['width'] );
+		if ( ! $args['width'] ) {
+			$args['width'] = $args['size'];
+		}
+	} else {
+		$args['width'] = $args['size'];
+	}
+
+	if ( empty( $args['default'] ) ) {
+		$args['default'] = get_option( 'avatar_default', 'mystery' );
+	}
+
+	switch ( $args['default'] ) {
+		case 'mm' :
+		case 'mystery' :
+		case 'mysteryman' :
+			$args['default'] = 'mm';
+			break;
+		case 'gravatar_default' :
+			$args['default'] = false;
+			break;
+	}
+
+	$args['force_default'] = (bool) $args['force_default'];
+
+	$args['rating'] = strtolower( $args['rating'] );
+
+	$args['found_avatar'] = false;
+
+	/**
+	 * Filter whether to retrieve the avatar URL early.
+	 *
+	 * Passing a non-null value in the 'url' member of the return array will
+	 * effectively short circuit get_avatar_data(), passing the value through
+	 * the {@see 'get_avatar_data'} filter and returning early.
+	 *
+	 * @since 4.2.0
+	 *
+	 * @param array             $args          Arguments passed to get_avatar_data(), after processing.
+	 * @param int|object|string $id_or_email   A user ID, email address, or comment object.
+	 */
+	$args = apply_filters( 'pre_get_avatar_data', $args, $id_or_email );
+
+	if ( isset( $args['url'] ) && ! is_null( $args['url'] ) ) {
+		/** This filter is documented in wp-includes/link-template.php */
+		return apply_filters( 'get_avatar_data', $args, $id_or_email );
+	}
+
+	$email_hash = '';
+	$user = $email = false;
+
+	// Process the user identifier.
+	if ( is_numeric( $id_or_email ) ) {
+		$user = get_user_by( 'id', absint( $id_or_email ) );
+	} elseif ( is_string( $id_or_email ) ) {
+		if ( strpos( $id_or_email, '@md5.gravatar.com' ) ) {
+			// md5 hash
+			list( $email_hash ) = explode( '@', $id_or_email );
+		} else {
+			// email address
+			$email = $id_or_email;
+		}
+	} elseif ( $id_or_email instanceof WP_User ) {
+		// User Object
+		$user = $id_or_email;
+	} elseif ( $id_or_email instanceof WP_Post ) {
+		// Post Object
+		$user = get_user_by( 'id', (int) $id_or_email->post_author );
+	} elseif ( is_object( $id_or_email ) && isset( $id_or_email->comment_ID ) ) {
+		// Comment Object
+
+		/**
+		 * Filter the list of allowed comment types for retrieving avatars.
+		 *
+		 * @since 3.0.0
+		 *
+		 * @param array $types An array of content types. Default only contains 'comment'.
+		 */
+		$allowed_comment_types = apply_filters( 'get_avatar_comment_types', array( 'comment' ) );
+		if ( ! empty( $id_or_email->comment_type ) && ! in_array( $id_or_email->comment_type, (array) $allowed_comment_types ) ) {
+			$args['url'] = false;
+			/** This filter is documented in wp-includes/link-template.php */
+			return apply_filters( 'get_avatar_data', $args, $id_or_email );
+		}
+
+		if ( ! empty( $id_or_email->user_id ) ) {
+			$user = get_user_by( 'id', (int) $id_or_email->user_id );
+		}
+		if ( ( ! $user || is_wp_error( $user ) ) && ! empty( $id_or_email->comment_author_email ) ) {
+			$email = $id_or_email->comment_author_email;
+		}
+	}
+
+	if ( ! $email_hash ) {
+		if ( $user ) {
+			$email = $user->user_email;
+		}
+
+		if ( $email ) {
+			$email_hash = md5( strtolower( trim( $email ) ) );
+		}
+	}
+
+	if ( $email_hash ) {
+		$args['found_avatar'] = true;
+		$gravatar_server = hexdec( $email_hash[0] ) % 3;
+	} else {
+		$gravatar_server = rand( 0, 2 );
+	}
+
+	$url_args = array(
+		's' => $args['size'],
+		'd' => $args['default'],
+		'f' => $args['force_default'] ? 'y' : false,
+		'r' => $args['rating'],
+	);
+
+	$url = sprintf( 'http://%d.gravatar.com/avatar/%s', $gravatar_server, $email_hash );
+
+	$url = add_query_arg(
+		rawurlencode_deep( array_filter( $url_args ) ),
+		set_url_scheme( $url, $args['scheme'] )
+	);
+
+	/**
+	 * Filter the avatar URL.
+	 *
+	 * @since 4.2.0
+	 *
+	 * @param string            $url         The URL of the avatar.
+	 * @param int|object|string $id_or_email A user ID, email address, or comment object.
+	 * @param array             $args        Arguments passed to get_avatar_data(), after processing.
+	 */
+	$args['url'] = apply_filters( 'get_avatar_url', $url, $id_or_email, $args );
+
+	/**
+	 * Filter the avatar data.
+	 *
+	 * @since 4.2.0
+	 *
+	 * @param array             $args        Arguments passed to get_avatar_data(), after processing.
+	 * @param int|object|string $id_or_email A user ID, email address, or comment object.
+	 */
+	return apply_filters( 'get_avatar_data', $args, $id_or_email );
+}