wp/wp-includes/comment-template.php
changeset 5 5e2f62d02dcd
parent 0 d970ebf37754
child 7 cf61fcea0001
--- a/wp/wp-includes/comment-template.php	Mon Jun 08 16:11:51 2015 +0000
+++ b/wp/wp-includes/comment-template.php	Tue Jun 09 03:35:32 2015 +0200
@@ -34,11 +34,14 @@
 	/**
 	 * Filter the returned comment author name.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
+	 * @since 4.1.0 The `$comment_ID` and `$comment` parameters were added.
 	 *
-	 * @param string $author The comment author's username.
+	 * @param string $author     The comment author's username.
+	 * @param int    $comment_ID The comment ID.
+	 * @param object $comment    The comment object.
 	 */
-	return apply_filters( 'get_comment_author', $author );
+	return apply_filters( 'get_comment_author', $author, $comment_ID, $comment );
 }
 
 /**
@@ -50,14 +53,17 @@
  */
 function comment_author( $comment_ID = 0 ) {
 	$author = get_comment_author( $comment_ID );
+
 	/**
 	 * Filter the comment author's name for display.
 	 *
-	 * @since 1.2.1
+	 * @since 1.2.0
+	 * @since 4.1.0 The `$comment_ID` parameter was added.
 	 *
-	 * @param string $author The comment author's username.
+	 * @param string $author     The comment author's username.
+	 * @param int    $comment_ID The comment ID.
 	 */
-	$author = apply_filters( 'comment_author', $author );
+	$author = apply_filters( 'comment_author', $author, $comment_ID );
 	echo $author;
 }
 
@@ -71,14 +77,18 @@
  */
 function get_comment_author_email( $comment_ID = 0 ) {
 	$comment = get_comment( $comment_ID );
+
 	/**
 	 * Filter the comment author's returned email address.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
+	 * @since 4.1.0 The `$comment_ID` and `$comment` parameters were added.
 	 *
-	 * @param string $comment->comment_author_email The comment author's email address.
+	 * @param string $comment_author_email The comment author's email address.
+	 * @param int    $comment_ID           The comment ID.
+	 * @param object $comment              The comment object.
 	 */
-	return apply_filters( 'get_comment_author_email', $comment->comment_author_email );
+	return apply_filters( 'get_comment_author_email', $comment->comment_author_email, $comment_ID, $comment );
 }
 
 /**
@@ -96,14 +106,17 @@
  */
 function comment_author_email( $comment_ID = 0 ) {
 	$author_email = get_comment_author_email( $comment_ID );
+
 	/**
 	 * Filter the comment author's email for display.
 	 *
-	 * @since 1.2.1
+	 * @since 1.2.0
+	 * @since 4.1.0 The `$comment_ID` parameter was added.
 	 *
 	 * @param string $author_email The comment author's email address.
+	 * @param int    $comment_ID   The comment ID.
 	 */
-	echo apply_filters( 'author_email', $author_email );
+	echo apply_filters( 'author_email', $author_email, $comment_ID );
 }
 
 /**
@@ -115,13 +128,12 @@
  * enable anyone, including those that people don't want to get the email
  * address and use it for their own means good and bad.
  *
- * @global object $comment The current Comment row object
-
  * @since 0.71
  *
- * @param string $linktext Optional. The text to display instead of the comment author's email address. Default empty.
- * @param string $before   Optional. The text or HTML to display before the email link.Default empty.
- * @param string $after    Optional. The text or HTML to display after the email link. Default empty.
+ * @param string $linktext Optional. Text to display instead of the comment author's email address.
+ *                         Default empty.
+ * @param string $before   Optional. Text or HTML to display before the email link. Default empty.
+ * @param string $after    Optional. Text or HTML to display after the email link. Default empty.
  */
 function comment_author_email_link( $linktext = '', $before = '', $after = '' ) {
 	if ( $link = get_comment_author_email_link( $linktext, $before, $after ) )
@@ -139,25 +151,29 @@
  *
  * @global object $comment The current Comment row object.
  *
- * @since 2.7
+ * @since 2.7.0
  *
- * @param string $linktext Optional. The text to display instead of the comment author's email address. Default empty.
- * @param string $before   Optional. The text or HTML to display before the email link. Default empty.
- * @param string $after    Optional. The text or HTML to display after the email link. Default empty.
+ * @param string $linktext Optional. Text to display instead of the comment author's email address.
+ *                         Default empty.
+ * @param string $before   Optional. Text or HTML to display before the email link. Default empty.
+ * @param string $after    Optional. Text or HTML to display after the email link. Default empty.
  */
 function get_comment_author_email_link( $linktext = '', $before = '', $after = '' ) {
 	global $comment;
+
 	/**
 	 * Filter the comment author's email for display.
 	 *
 	 * Care should be taken to protect the email address and assure that email
-	 * harvesters do not capture your commentors' email address.
+	 * harvesters do not capture your commenter's email address.
 	 *
-	 * @since 1.2.1
+	 * @since 1.2.0
+	 * @since 4.1.0 The `$comment` parameter was added.
 	 *
-	 * @param string $comment->comment_author_email The comment author's email address.
+	 * @param string $comment_author_email The comment author's email address.
+	 * @param object $comment              The comment object.
 	 */
-	$email = apply_filters( 'comment_email', $comment->comment_author_email );
+	$email = apply_filters( 'comment_email', $comment->comment_author_email, $comment );
 	if ((!empty($email)) && ($email != '@')) {
 	$display = ($linktext != '') ? $linktext : $email;
 		$return  = $before;
@@ -177,7 +193,8 @@
  *
  * @since 1.5.0
  *
- * @param int $comment_ID Optional. The ID of the comment for which to get the author's link. Default current comment.
+ * @param int $comment_ID ID of the comment for which to get the author's link.
+ *                        Default current comment.
  * @return string The comment author name or HTML link for author's URL.
  */
 function get_comment_author_link( $comment_ID = 0 ) {
@@ -192,20 +209,26 @@
 	/**
 	 * Filter the comment author's link for display.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
+	 * @since 4.1.0 The `$author` and `$comment_ID` parameters were added.
 	 *
-	 * @param string $return The HTML-formatted comment author link. Empty for an invalid URL.
+	 * @param string $return     The HTML-formatted comment author link.
+	 *                           Empty for an invalid URL.
+	 * @param string $author     The comment author's username.
+	 * @param int    $comment_ID The comment ID.
 	 */
-	return apply_filters( 'get_comment_author_link', $return );
+	return apply_filters( 'get_comment_author_link', $return, $author, $comment_ID );
 }
 
 /**
  * Display the html link to the url of the author of the current comment.
  *
  * @since 0.71
+ *
  * @see get_comment_author_link() Echoes result
  *
- * @param int $comment_ID Optional. The ID of the comment for which to print the author's link. Default current comment.
+ * @param int $comment_ID ID of the comment for which to print the author's
+ *                        link. Default current comment.
  */
 function comment_author_link( $comment_ID = 0 ) {
 	echo get_comment_author_link( $comment_ID );
@@ -216,8 +239,9 @@
  *
  * @since 1.5.0
  *
- * @param int $comment_ID Optional. The ID of the comment for which to get the author's IP address. Default current comment.
- * @return string The comment author's IP address.
+ * @param int $comment_ID ID of the comment for which to get the author's IP
+ *                        address. Default current comment.
+ * @return string Comment author's IP address.
  */
 function get_comment_author_IP( $comment_ID = 0 ) {
 	$comment = get_comment( $comment_ID );
@@ -225,11 +249,14 @@
 	/**
 	 * Filter the comment author's returned IP address.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
+	 * @since 4.1.0 The `$comment_ID` and `$comment` parameters were added.
 	 *
-	 * @param string $comment->comment_author_IP The comment author's IP address.
+	 * @param string $comment_author_IP The comment author's IP address.
+	 * @param int    $comment_ID        The comment ID.
+	 * @param object $comment           The comment object.
 	 */
-	return apply_filters( 'get_comment_author_IP', $comment->comment_author_IP );
+	return apply_filters( 'get_comment_author_IP', $comment->comment_author_IP, $comment_ID, $comment );
 }
 
 /**
@@ -237,7 +264,8 @@
  *
  * @since 0.71
  *
- * @param int $comment_ID Optional. The ID of the comment for which to print the author's IP address. Default current comment.
+ * @param int $comment_ID ID of the comment for which to print the author's IP
+ *                        address. Default current comment.
  */
 function comment_author_IP( $comment_ID = 0 ) {
 	echo get_comment_author_IP( $comment_ID );
@@ -248,14 +276,26 @@
  *
  * @since 1.5.0
  *
- * @param int $comment_ID Optional. The ID of the comment for which to get the author's URL. Default current comment.
+ * @param int $comment_ID ID of the comment for which to get the author's URL.
+ *                        Default current comment.
  * @return string
  */
 function get_comment_author_url( $comment_ID = 0 ) {
 	$comment = get_comment( $comment_ID );
 	$url = ('http://' == $comment->comment_author_url) ? '' : $comment->comment_author_url;
 	$url = esc_url( $url, array('http', 'https') );
-	return apply_filters('get_comment_author_url', $url);
+
+	/**
+	 * Filter the comment author's URL.
+	 *
+	 * @since 1.5.0
+	 * @since 4.1.0 The `$comment_ID` and `$comment` parameters were added.
+	 *
+	 * @param string $url        The comment author's URL.
+	 * @param int    $comment_ID The comment ID.
+	 * @param object $comment    The comment object.
+	 */
+	return apply_filters( 'get_comment_author_url', $url, $comment_ID, $comment );
 }
 
 /**
@@ -263,18 +303,22 @@
  *
  * @since 0.71
  *
- * @param int $comment_ID Optional. The ID of the comment for which to print the author's URL. Default current comment.
+ * @param int $comment_ID ID of the comment for which to print the author's URL.
+ *                        Default current comment.
  */
 function comment_author_url( $comment_ID = 0 ) {
 	$author_url = get_comment_author_url( $comment_ID );
+
 	/**
 	 * Filter the comment author's URL for display.
 	 *
-	 * @since 1.2.1
+	 * @since 1.2.0
+	 * @since 4.1.0 The `$comment_ID` parameter was added.
 	 *
 	 * @param string $author_url The comment author's URL.
+	 * @param int    $comment_ID The comment ID.
 	 */
-	echo apply_filters( 'comment_url', $author_url );
+	echo apply_filters( 'comment_url', $author_url, $comment_ID );
 }
 
 /**
@@ -289,9 +333,12 @@
  *
  * @since 1.5.0
  *
- * @param string $linktext Optional. The text to display instead of the comment author's email address. Default empty.
- * @param string $before   Optional. The text or HTML to display before the email link. Default empty.
- * @param string $after    Optional. The text or HTML to display after the email link. Default empty.
+ * @param string $linktext Optional. The text to display instead of the comment
+ *                         author's email address. Default empty.
+ * @param string $before   Optional. The text or HTML to display before the email link.
+ *                         Default empty.
+ * @param string $after    Optional. The text or HTML to display after the email link.
+ *                         Default empty.
  * @return string The HTML link between the $before and $after parameters.
  */
 function get_comment_author_url_link( $linktext = '', $before = '', $after = '' ) {
@@ -299,14 +346,17 @@
 	$display = ($linktext != '') ? $linktext : $url;
 	$display = str_replace( 'http://www.', '', $display );
 	$display = str_replace( 'http://', '', $display );
-	if ( '/' == substr($display, -1) )
+
+	if ( '/' == substr($display, -1) ) {
 		$display = substr($display, 0, -1);
+	}
+
 	$return = "$before<a href='$url' rel='external'>$display</a>$after";
 
 	/**
 	 * Filter the comment author's returned URL link.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
 	 *
 	 * @param string $return The HTML-formatted comment author URL link.
 	 */
@@ -318,23 +368,28 @@
  *
  * @since 0.71
  *
- * @param string $linktext Optional. The text to display instead of the comment author's email address. Default empty.
- * @param string $before   Optional. The text or HTML to display before the email link. Default empty.
- * @param string $after    Optional. The text or HTML to display after the email link. Default empty.
+ * @param string $linktext Optional. Text to display instead of the comment author's
+ *                         email address. Default empty.
+ * @param string $before   Optional. Text or HTML to display before the email link.
+ *                         Default empty.
+ * @param string $after    Optional. Text or HTML to display after the email link.
+ *                         Default empty.
  */
 function comment_author_url_link( $linktext = '', $before = '', $after = '' ) {
 	echo get_comment_author_url_link( $linktext, $before, $after );
 }
 
 /**
- * Generates semantic classes for each comment element
+ * Generates semantic classes for each comment element.
  *
  * @since 2.7.0
  *
- * @param string|array $class      Optional. One or more classes to add to the class list. Default empty.
- * @param int          $comment_id Optional. Comment ID. Default current comment.
- * @param int|WP_Post  $post_id    Optional. Post ID or WP_Post object. Default current post.
- * @param bool         $echo       Optional. Whether comment_class should echo or return. Default true.
+ * @param string|array $class      Optional. One or more classes to add to the class list.
+ *                                 Default empty.
+ * @param int          $comment_id Comment ID. Default current comment.
+ * @param int|WP_Post  $post_id    Post ID or WP_Post object. Default current post.
+ * @param bool         $echo       Optional. Whether to cho or return the output.
+ *                                 Default true.
  */
 function comment_class( $class = '', $comment_id = null, $post_id = null, $echo = true ) {
 	// Separates classes with a single space, collates classes for comment DIV
@@ -346,13 +401,13 @@
 }
 
 /**
- * Returns the classes for the comment div as an array
+ * Returns the classes for the comment div as an array.
  *
  * @since 2.7.0
  *
  * @param string|array $class      Optional. One or more classes to add to the class list. Default empty.
- * @param int          $comment_id Optional. Comment ID. Default current comment.
- * @param int|WP_Post  $post_id    Optional. Post ID or WP_Post object. Default current post.
+ * @param int          $comment_id Comment ID. Default current comment.
+ * @param int|WP_Post  $post_id    Post ID or WP_Post object. Default current post.
  * @return array An array of classes.
  */
 function get_comment_class( $class = '', $comment_id = null, $post_id = null ) {
@@ -365,15 +420,15 @@
 	// Get the comment type (comment, trackback),
 	$classes[] = ( empty( $comment->comment_type ) ) ? 'comment' : $comment->comment_type;
 
-	// If the comment author has an id (registered), then print the log in name
-	if ( $comment->user_id > 0 && $user = get_userdata($comment->user_id) ) {
-		// For all registered users, 'byuser'
+	// Add classes for comment authors that are registered users.
+	if ( $comment->user_id > 0 && $user = get_userdata( $comment->user_id ) ) {
 		$classes[] = 'byuser';
-		$classes[] = 'comment-author-' . sanitize_html_class($user->user_nicename, $comment->user_id);
+		$classes[] = 'comment-author-' . sanitize_html_class( $user->user_nicename, $comment->user_id );
 		// For comment authors who are the author of the post
 		if ( $post = get_post($post_id) ) {
-			if ( $comment->user_id === $post->post_author )
+			if ( $comment->user_id === $post->post_author ) {
 				$classes[] = 'bypostauthor';
+			}
 		}
 	}
 
@@ -422,9 +477,10 @@
 	 * @param array       $classes    An array of comment classes.
 	 * @param string      $class      A comma-separated list of additional classes added to the list.
 	 * @param int         $comment_id The comment id.
+	 * @param object   	  $comment    The comment
 	 * @param int|WP_Post $post_id    The post ID or WP_Post object.
 	 */
-	return apply_filters( 'comment_class', $classes, $class, $comment_id, $post_id );
+	return apply_filters( 'comment_class', $classes, $class, $comment_id, $comment, $post_id );
 }
 
 /**
@@ -433,7 +489,7 @@
  * @since 1.5.0
  *
  * @param string $d          Optional. The format of the date. Default user's setting.
- * @param int    $comment_ID Optional. The ID of the comment for which to get the date. Default current comment.
+ * @param int    $comment_ID ID of the comment for which to get the date. Default current comment.
  * @return string The comment's date.
  */
 function get_comment_date( $d = '', $comment_ID = 0 ) {
@@ -445,12 +501,13 @@
 	/**
 	 * Filter the returned comment date.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
 	 *
-	 * @param string|int $date Formatted date string or Unix timestamp.
-	 * @param string     $d    The format of the date.
+	 * @param string|int $date    Formatted date string or Unix timestamp.
+	 * @param string     $d       The format of the date.
+	 * @param object     $comment The comment object.
 	 */
-	return apply_filters( 'get_comment_date', $date, $d );
+	return apply_filters( 'get_comment_date', $date, $d, $comment );
 }
 
 /**
@@ -459,7 +516,7 @@
  * @since 0.71
  *
  * @param string $d          Optional. The format of the date. Default user's settings.
- * @param int    $comment_ID Optional. The ID of the comment for which to print the date. Default current comment.
+ * @param int    $comment_ID ID of the comment for which to print the date. Default current comment.
  */
 function comment_date( $d = '', $comment_ID = 0 ) {
 	echo get_comment_date( $d, $comment_ID );
@@ -474,13 +531,15 @@
  *
  * @since 1.5.0
  *
- * @param int $comment_ID Optional. The ID of the comment for which to get the excerpt. Default current comment.
+ * @param int $comment_ID ID of the comment for which to get the excerpt.
+ *                        Default current comment.
  * @return string The maybe truncated comment with 20 words or less.
  */
 function get_comment_excerpt( $comment_ID = 0 ) {
 	$comment = get_comment( $comment_ID );
 	$comment_text = strip_tags($comment->comment_content);
 	$blah = explode(' ', $comment_text);
+
 	if (count($blah) > 20) {
 		$k = 20;
 		$use_dotdotdot = 1;
@@ -488,12 +547,24 @@
 		$k = count($blah);
 		$use_dotdotdot = 0;
 	}
+
 	$excerpt = '';
 	for ($i=0; $i<$k; $i++) {
 		$excerpt .= $blah[$i] . ' ';
 	}
 	$excerpt .= ($use_dotdotdot) ? '&hellip;' : '';
-	return apply_filters('get_comment_excerpt', $excerpt);
+
+	/**
+	 * Filter the retrieved comment excerpt.
+	 *
+	 * @since 1.5.0
+	 * @since 4.1.0 The `$comment_ID` and `$comment` parameters were added.
+	 *
+	 * @param string $excerpt    The comment excerpt text.
+	 * @param int    $comment_ID The comment ID.
+	 * @param object $comment    The comment object.
+	 */
+	return apply_filters( 'get_comment_excerpt', $excerpt, $comment_ID, $comment );
 }
 
 /**
@@ -501,18 +572,22 @@
  *
  * @since 1.2.0
  *
- * @param int $comment_ID Optional. The ID of the comment for which to print the excerpt. Default current comment.
+ * @param int $comment_ID ID of the comment for which to print the excerpt.
+ *                        Default current comment.
  */
 function comment_excerpt( $comment_ID = 0 ) {
 	$comment_excerpt = get_comment_excerpt($comment_ID);
+
 	/**
 	 * Filter the comment excerpt for display.
 	 *
-	 * @since 1.2.1
+	 * @since 1.2.0
+	 * @since 4.1.0 The `$comment_ID` parameter was added.
 	 *
 	 * @param string $comment_excerpt The comment excerpt text.
+	 * @param int    $comment_ID      The comment ID.
 	 */
-	echo apply_filters( 'comment_excerpt', $comment_excerpt );
+	echo apply_filters( 'comment_excerpt', $comment_excerpt, $comment_ID );
 }
 
 /**
@@ -524,14 +599,17 @@
  */
 function get_comment_ID() {
 	global $comment;
+
 	/**
 	 * Filter the returned comment ID.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
+	 * @since 4.1.0 The `$comment_ID` parameter was added.
 	 *
-	 * @param int $comment->comment_ID The current comment ID.
+	 * @param int    $comment_ID The current comment ID.
+	 * @param object $comment    The comment object.
 	 */
-	return apply_filters( 'get_comment_ID', $comment->comment_ID );
+	return apply_filters( 'get_comment_ID', $comment->comment_ID, $comment );
 }
 
 /**
@@ -548,8 +626,10 @@
  *
  * @since 1.5.0
  *
- * @param mixed $comment Optional. Comment to retrieve. Default current comment.
- * @param array $args    Optional. An array of arguments to override the defaults. @see get_page_of_comment()
+ * @see get_page_of_comment()
+ *
+ * @param mixed $comment Comment to retrieve. Default current comment.
+ * @param array $args    Optional. An array of arguments to override the defaults.
  * @return string The permalink to the given comment.
  */
 function get_comment_link( $comment = null, $args = array() ) {
@@ -558,10 +638,8 @@
 	$comment = get_comment($comment);
 
 	// Backwards compat
-	if ( !is_array($args) ) {
-		$page = $args;
-		$args = array();
-		$args['page'] = $page;
+	if ( ! is_array( $args ) ) {
+		$args = array( 'page' => $args );
 	}
 
 	$defaults = array( 'type' => 'all', 'page' => '', 'per_page' => '', 'max_depth' => '' );
@@ -580,7 +658,7 @@
 			$args['page'] = ( !empty($in_comment_loop) ) ? get_query_var('cpage') : get_page_of_comment( $comment->comment_ID, $args );
 
 		if ( $wp_rewrite->using_permalinks() )
-			$link = user_trailingslashit( trailingslashit( get_permalink( $comment->comment_post_ID ) ) . 'comment-page-' . $args['page'], 'comment' );
+			$link = user_trailingslashit( trailingslashit( get_permalink( $comment->comment_post_ID ) ) . $wp_rewrite->comments_pagination_base . '-' . $args['page'], 'comment' );
 		else
 			$link = add_query_arg( 'cpage', $args['page'], get_permalink( $comment->comment_post_ID ) );
 	} else {
@@ -593,9 +671,11 @@
 	 *
 	 * @since 2.8.0
 	 *
+	 * @see get_page_of_comment()
+	 *
 	 * @param string $link    The comment permalink with '#comment-$id' appended.
 	 * @param object $comment The current comment object.
-	 * @param array  $args    An array of arguments to override the defaults. @see get_page_of_comment()
+	 * @param array  $args    An array of arguments to override the defaults.
 	 */
 	return apply_filters( 'get_comment_link', $link, $comment, $args );
 }
@@ -605,7 +685,7 @@
  *
  * @since 1.5.0
  *
- * @param int|WP_Post $post_id Optional. Post ID or WP_Post object. Default current post.
+ * @param int|WP_Post $post_id Optional. Post ID or WP_Post object. Default is global $post.
  * @return string The link to the comments.
  */
 function get_comments_link( $post_id = 0 ) {
@@ -613,10 +693,10 @@
 	/**
 	 * Filter the returned post comments permalink.
 	 *
-	 * @since
+	 * @since 3.6.0
 	 *
-	 * @param string      $comments_link The post comments permalink with '#comments' appended.
-	 * @param int|WP_Post $post_id       The post ID or WP_Post object.
+	 * @param string      $comments_link Post comments permalink with '#comments' appended.
+	 * @param int|WP_Post $post_id       Post ID or WP_Post object.
 	 */
 	return apply_filters( 'get_comments_link', $comments_link, $post_id );
 }
@@ -627,7 +707,7 @@
  * @since 0.71
  *
  * @param string $deprecated   Not Used.
- * @param bool   $deprecated_2 Not Used.
+ * @param string $deprecated_2 Not Used.
  */
 function comments_link( $deprecated = '', $deprecated_2 = '' ) {
 	if ( !empty( $deprecated ) )
@@ -642,28 +722,26 @@
  *
  * @since 1.5.0
  *
- * @param int|WP_Post $post_id Optional. Post ID or WP_Post object. Default current post.
+ * @param int|WP_Post $post_id Optional. Post ID or WP_Post object. Default is global $post.
  * @return int The number of comments a post has.
  */
 function get_comments_number( $post_id = 0 ) {
-	$post_id = absint( $post_id );
-
-	if ( !$post_id )
-		$post_id = get_the_ID();
+	$post = get_post( $post_id );
 
-	$post = get_post($post_id);
-	if ( ! isset($post->comment_count) )
+	if ( ! $post ) {
 		$count = 0;
-	else
+	} else {
 		$count = $post->comment_count;
+		$post_id = $post->ID;
+	}
 
 	/**
 	 * Filter the returned comment count for a post.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
 	 *
-	 * @param int         $count   The number of comments a post has.
-	 * @param int|WP_Post $post_id The post ID or WP_Post object.
+	 * @param int $count   Number of comments a post has.
+	 * @param int $post_id Post ID.
 	 */
 	return apply_filters( 'get_comments_number', $count, $post_id );
 }
@@ -679,27 +757,43 @@
  * @param string $deprecated Not used.
  */
 function comments_number( $zero = false, $one = false, $more = false, $deprecated = '' ) {
-	if ( !empty( $deprecated ) )
+	if ( ! empty( $deprecated ) ) {
 		_deprecated_argument( __FUNCTION__, '1.3' );
+	}
+	echo get_comments_number_text( $zero, $one, $more );
+}
 
+/**
+ * Display the language string for the number of comments the current post has.
+ *
+ * @since 4.0.0
+ *
+ * @param string $zero Optional. Text for no comments. Default false.
+ * @param string $one  Optional. Text for one comment. Default false.
+ * @param string $more Optional. Text for more than one comment. Default false.
+ */
+function get_comments_number_text( $zero = false, $one = false, $more = false ) {
 	$number = get_comments_number();
 
-	if ( $number > 1 )
-		$output = str_replace('%', number_format_i18n($number), ( false === $more ) ? __('% Comments') : $more);
-	elseif ( $number == 0 )
-		$output = ( false === $zero ) ? __('No Comments') : $zero;
-	else // must be one
-		$output = ( false === $one ) ? __('1 Comment') : $one;
-
+	if ( $number > 1 ) {
+		$output = str_replace( '%', number_format_i18n( $number ), ( false === $more ) ? __( '% Comments' ) : $more );
+	} elseif ( $number == 0 ) {
+		$output = ( false === $zero ) ? __( 'No Comments' ) : $zero;
+	} else { // must be one
+		$output = ( false === $one ) ? __( '1 Comment' ) : $one;
+	}
 	/**
 	 * Filter the comments count for display.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
 	 *
-	 * @param string $output A translatable string formatted based on whether the count is equal to 0, 1, or 1+. @see _n()
+	 * @see _n()
+	 *
+	 * @param string $output A translatable string formatted based on whether the count
+	 *                       is equal to 0, 1, or 1+.
 	 * @param int    $number The number of post comments.
 	 */
-	echo apply_filters( 'comments_number', $output, $number );
+	return apply_filters( 'comments_number', $output, $number );
 }
 
 /**
@@ -707,8 +801,10 @@
  *
  * @since 1.5.0
  *
- * @param int   $comment_ID Optional. The ID of the comment for which to get the text. Default current comment.
- * @param array $args       Optional. An array of arguments. @see Walker_Comment::comment()
+ * @see Walker_Comment::comment()
+ *
+ * @param int   $comment_ID ID of the comment for which to get the text. Default current comment.
+ * @param array $args       Optional. An array of arguments. Default empty.
  * @return string The comment content.
  */
 function get_comment_text( $comment_ID = 0, $args = array() ) {
@@ -717,11 +813,13 @@
 	/**
 	 * Filter the text of a comment.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
+	 *
+	 * @see Walker_Comment::comment()
 	 *
-	 * @param string $comment->comment_content The text of the comment.
-	 * @param object $comment                  The comment object.
-	 * @param array  $args                     An array of arguments. @see Walker_Comment::comment()
+	 * @param string $comment_content Text of the comment.
+	 * @param object $comment         The comment object.
+	 * @param array  $args            An array of arguments.
 	 */
 	return apply_filters( 'get_comment_text', $comment->comment_content, $comment, $args );
 }
@@ -731,10 +829,10 @@
  *
  * @since 0.71
  *
- * @param int   $comment_ID Optional. The ID of the comment for which to print the text.
- *                          Default 0.
- * @param array $args       Optional. An array of arguments. @see Walker_Comment::comment()
- *                          Default empty array.
+ * @see Walker_Comment::comment()
+ *
+ * @param int   $comment_ID ID of the comment for which to print the text. Default 0.
+ * @param array $args       Optional. An array of arguments. Default empty array. Default empty.
  */
 function comment_text( $comment_ID = 0, $args = array() ) {
 	$comment = get_comment( $comment_ID );
@@ -743,11 +841,13 @@
 	/**
 	 * Filter the text of a comment to be displayed.
 	 *
-	 * @since 1.2.1
+	 * @since 1.2.0
+	 *
+	 * @see Walker_Comment::comment()
 	 *
-	 * @param string $comment_text The text of the current comment.
+	 * @param string $comment_text Text of the current comment.
 	 * @param object $comment      The comment object.
-	 * @param array  $args         An array of arguments. @see Walker_Comment::comment()
+	 * @param array  $args         An array of arguments.
 	 */
 	echo apply_filters( 'comment_text', $comment_text, $comment, $args );
 }
@@ -759,8 +859,9 @@
  *
  * @param string $d         Optional. The format of the time. Default user's settings.
  * @param bool   $gmt       Optional. Whether to use the GMT date. Default false.
- * @param bool   $translate Optional. Whether to translate the time (for use in feeds). Default true.
- * @return string The formatted time
+ * @param bool   $translate Optional. Whether to translate the time (for use in feeds).
+ *                          Default true.
+ * @return string The formatted time.
  */
 function get_comment_time( $d = '', $gmt = false, $translate = true ) {
 	global $comment;
@@ -773,14 +874,15 @@
 	/**
 	 * Filter the returned comment time.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
 	 *
 	 * @param string|int $date      The comment time, formatted as a date string or Unix timestamp.
-	 * @param string     $d         The date format.
+	 * @param string     $d         Date format.
 	 * @param bool       $gmt       Whether the GMT date is in use.
 	 * @param bool       $translate Whether the time is translated.
+	 * @param object     $comment   The comment object.
 	 */
-	return apply_filters( 'get_comment_time', $date, $d, $gmt, $translate );
+	return apply_filters( 'get_comment_time', $date, $d, $gmt, $translate, $comment );
 }
 
 /**
@@ -799,8 +901,8 @@
  *
  * @since 1.5.0
  *
- * @param int $comment_ID Optional. The ID of the comment for which to get the type. Default current comment.
- * @return string The comment type
+ * @param int $comment_ID ID of the comment for which to get the type. Default current comment.
+ * @return string The comment type.
  */
 function get_comment_type( $comment_ID = 0 ) {
 	$comment = get_comment( $comment_ID );
@@ -810,11 +912,14 @@
 	/**
 	 * Filter the returned comment type.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.0
+	 * @since 4.1.0 The `$comment_ID` and `$comment` parameters were added.
 	 *
-	 * @param string $comment->comment_type The type of comment, such as 'comment', 'pingback', or 'trackback'.
+	 * @param string $comment_type The type of comment, such as 'comment', 'pingback', or 'trackback'.
+	 * @param int 	 $comment_ID   The comment ID.
+	 * @param object $comment      The comment object.
 	 */
-	return apply_filters( 'get_comment_type', $comment->comment_type );
+	return apply_filters( 'get_comment_type', $comment->comment_type, $comment_ID, $comment );
 }
 
 /**
@@ -822,9 +927,9 @@
  *
  * @since 0.71
  *
- * @param string $commenttxt   Optional. The string to display for comment type. Default false.
- * @param string $trackbacktxt Optional. The string to display for trackback type. Default false.
- * @param string $pingbacktxt  Optional. The string to display for pingback type. Default false.
+ * @param string $commenttxt   Optional. String to display for comment type. Default false.
+ * @param string $trackbacktxt Optional. String to display for trackback type. Default false.
+ * @param string $pingbacktxt  Optional. String to display for pingback type. Default false.
  */
 function comment_type( $commenttxt = false, $trackbacktxt = false, $pingbacktxt = false ) {
 	if ( false === $commenttxt ) $commenttxt = _x( 'Comment', 'noun' );
@@ -876,7 +981,8 @@
  * @since 0.71
  *
  * @param bool $deprecated_echo Not used.
- * @return void|string Should only be used to echo the trackback URL, use get_trackback_url() for the result instead.
+ * @return void|string Should only be used to echo the trackback URL, use get_trackback_url()
+ *                     for the result instead.
  */
 function trackback_url( $deprecated_echo = true ) {
 	if ( $deprecated_echo !== true )
@@ -897,11 +1003,13 @@
  * @param int $deprecated Not used (Was $timezone = 0).
  */
 function trackback_rdf( $deprecated = '' ) {
-	if ( !empty( $deprecated ) )
+	if ( ! empty( $deprecated ) ) {
 		_deprecated_argument( __FUNCTION__, '2.5' );
+	}
 
-	if ( false !== stripos($_SERVER['HTTP_USER_AGENT'], 'W3C_Validator') )
+	if ( isset( $_SERVER['HTTP_USER_AGENT'] ) && false !== stripos( $_SERVER['HTTP_USER_AGENT'], 'W3C_Validator' ) ) {
 		return;
+	}
 
 	echo '<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
 			xmlns:dc="http://purl.org/dc/elements/1.1/"
@@ -922,7 +1030,7 @@
  *
  * @since 1.5.0
  *
- * @param int|WP_Post $post_id Optional. Post ID or WP_Post object. Default current post.
+ * @param int|WP_Post $post_id Post ID or WP_Post object. Default current post.
  * @return bool True if the comments are open.
  */
 function comments_open( $post_id = null ) {
@@ -934,7 +1042,7 @@
 	/**
 	 * Filter whether the current post is open for comments.
 	 *
-	 * @since
+	 * @since 2.5.0
 	 *
 	 * @param bool        $open    Whether the current post is open for comments.
 	 * @param int|WP_Post $post_id The post ID or WP_Post object.
@@ -947,7 +1055,7 @@
  *
  * @since 1.5.0
  *
- * @param int|WP_Post $post_id Optional. Post ID or WP_Post object. Default current post.
+ * @param int|WP_Post $post_id Post ID or WP_Post object. Default current post.
  * @return bool True if pings are accepted
  */
 function pings_open( $post_id = null ) {
@@ -955,6 +1063,15 @@
 	$_post = get_post($post_id);
 
 	$open = ( 'open' == $_post->ping_status );
+
+	/**
+	 * Filter whether the current post is open for pings.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param bool        $open    Whether the current post is open for pings.
+	 * @param int|WP_Post $post_id The post ID or WP_Post object.
+	 */
 	return apply_filters( 'pings_open', $open, $post_id );
 }
 
@@ -1004,7 +1121,8 @@
  * @since 1.5.0
  *
  * @param string $file              Optional. The file to load. Default '/comments.php'.
- * @param bool   $separate_comments Optional. Whether to separate the comments by comment type. Default false.
+ * @param bool   $separate_comments Optional. Whether to separate the comments by comment type.
+ *                                  Default false.
  * @return null Returns null if no comments appear.
  */
 function comments_template( $file = '/comments.php', $separate_comments = false ) {
@@ -1018,45 +1136,50 @@
 
 	$req = get_option('require_name_email');
 
-	/**
+	/*
 	 * Comment author information fetched from the comment cookies.
-	 *
-	 * @uses wp_get_current_commenter()
 	 */
 	$commenter = wp_get_current_commenter();
 
-	/**
+	/*
 	 * The name of the current comment author escaped for use in attributes.
+	 * Escaped by sanitize_comment_cookies().
 	 */
-	$comment_author = $commenter['comment_author']; // Escaped by sanitize_comment_cookies()
+	$comment_author = $commenter['comment_author'];
 
-	/**
+	/*
 	 * The email address of the current comment author escaped for use in attributes.
+	 * Escaped by sanitize_comment_cookies().
 	 */
-	$comment_author_email = $commenter['comment_author_email'];  // Escaped by sanitize_comment_cookies()
+	$comment_author_email = $commenter['comment_author_email'];
 
-	/**
+	/*
 	 * The url of the current comment author escaped for use in attributes.
 	 */
 	$comment_author_url = esc_url($commenter['comment_author_url']);
 
-	/** @todo Use API instead of SELECTs. */
-	if ( $user_ID) {
-		$comments = $wpdb->get_results($wpdb->prepare("SELECT * FROM $wpdb->comments WHERE comment_post_ID = %d AND (comment_approved = '1' OR ( user_id = %d AND comment_approved = '0' ) )  ORDER BY comment_date_gmt", $post->ID, $user_ID));
-	} else if ( empty($comment_author) ) {
-		$comments = get_comments( array('post_id' => $post->ID, 'status' => 'approve', 'order' => 'ASC') );
-	} else {
-		$comments = $wpdb->get_results($wpdb->prepare("SELECT * FROM $wpdb->comments WHERE comment_post_ID = %d AND ( comment_approved = '1' OR ( comment_author = %s AND comment_author_email = %s AND comment_approved = '0' ) ) ORDER BY comment_date_gmt", $post->ID, wp_specialchars_decode($comment_author,ENT_QUOTES), $comment_author_email));
+	$comment_args = array(
+		'order'   => 'ASC',
+		'orderby' => 'comment_date_gmt',
+		'status'  => 'approve',
+		'post_id' => $post->ID,
+	);
+
+	if ( $user_ID ) {
+		$comment_args['include_unapproved'] = array( $user_ID );
+	} elseif ( ! empty( $comment_author_email ) ) {
+		$comment_args['include_unapproved'] = array( $comment_author_email );
 	}
 
-	// keep $comments for legacy's sake
+	$comments = get_comments( $comment_args );
+
 	/**
 	 * Filter the comments array.
 	 *
 	 * @since 2.1.0
 	 *
-	 * @param array $comments The array of comments supplied to the comments template.
-	 * @param int   $post->ID The post ID.
+	 * @param array $comments Array of comments supplied to the comments template.
+	 * @param int   $post_ID  Post ID.
 	 */
 	$wp_query->comments = apply_filters( 'comments_array', $comments, $post->ID );
 	$comments = &$wp_query->comments;
@@ -1081,7 +1204,7 @@
 	/**
 	 * Filter the path to the theme template file used for the comments template.
 	 *
-	 * @since 1.5.2
+	 * @since 1.5.1
 	 *
 	 * @param string $theme_template The path to the theme template file.
 	 */
@@ -1129,32 +1252,51 @@
 /**
  * Displays the link to the comments popup window for the current post ID.
  *
- * Is not meant to be displayed on single posts and pages. Should be used on the
- * lists of posts
+ * Is not meant to be displayed on single posts and pages. Should be used
+ * on the lists of posts
  *
  * @global string $wpcommentspopupfile  The URL to use for the popup window.
  * @global int    $wpcommentsjavascript Whether to use JavaScript. Set when function is called.
  *
  * @since 0.71
  *
- * @param string $zero      Optional. The string to display when no comments. Default false.
- * @param string $one       Optional. The string to display when only one comment is available. Default false.
- * @param string $more      Optional. The string to display when there are more than one comment. Default false.
- * @param string $css_class Optional. The CSS class to use for comments. Default empty.
- * @param string $none      Optional. The string to display when comments have been turned off. Default false.
+ * @param string $zero      Optional. String to display when no comments. Default false.
+ * @param string $one       Optional. String to display when only one comment is available.
+ *                          Default false.
+ * @param string $more      Optional. String to display when there are more than one comment.
+ *                          Default false.
+ * @param string $css_class Optional. CSS class to use for comments. Default empty.
+ * @param string $none      Optional. String to display when comments have been turned off.
+ *                          Default false.
  * @return null Returns null on single posts and pages.
  */
 function comments_popup_link( $zero = false, $one = false, $more = false, $css_class = '', $none = false ) {
 	global $wpcommentspopupfile, $wpcommentsjavascript;
 
 	$id = get_the_ID();
+	$title = get_the_title();
+	$number = get_comments_number( $id );
 
-	if ( false === $zero ) $zero = __( 'No Comments' );
-	if ( false === $one ) $one = __( '1 Comment' );
-	if ( false === $more ) $more = __( '% Comments' );
-	if ( false === $none ) $none = __( 'Comments Off' );
+	if ( false === $zero ) {
+		/* translators: %s: post title */
+		$zero = sprintf( __( 'No Comments<span class="screen-reader-text"> on %s</span>' ), $title );
+	}
+
+	if ( false === $one ) {
+		/* translators: %s: post title */
+		$one = sprintf( __( '1 Comment<span class="screen-reader-text"> on %s</span>' ), $title );
+	}
 
-	$number = get_comments_number( $id );
+	if ( false === $more ) {
+		/* translators: 1: Number of comments 2: post title */
+		$more = _n( '%1$s Comment<span class="screen-reader-text"> on %2$s</span>', '%1$s Comments<span class="screen-reader-text"> on %2$s</span>', $number );
+		$more = sprintf( $more, number_format_i18n( $number ), $title );
+	}
+
+	if ( false === $none ) {
+		/* translators: %s: post title */
+		$none = sprintf( __( 'Comments Off<span class="screen-reader-text"> on %s</span>' ), $title );
+	}
 
 	if ( 0 == $number && !comments_open() && !pings_open() ) {
 		echo '<span' . ((!empty($css_class)) ? ' class="' . esc_attr( $css_class ) . '"' : '') . '>' . $none . '</span>';
@@ -1185,7 +1327,6 @@
 	if ( !empty( $css_class ) ) {
 		echo ' class="'.$css_class.'" ';
 	}
-	$title = the_title_attribute( array('echo' => 0 ) );
 
 	$attributes = '';
 	/**
@@ -1197,7 +1338,7 @@
 	 */
 	echo apply_filters( 'comments_popup_link_attributes', $attributes );
 
-	echo ' title="' . esc_attr( sprintf( __('Comment on %s'), $title ) ) . '">';
+	echo '>';
 	comments_number( $zero, $one, $more );
 	echo '</a>';
 }
@@ -1210,70 +1351,95 @@
  * @param array $args {
  *     Optional. Override default arguments.
  *
- *     @type string 'add_below'  The first part of the selector used to identify the comment to respond below. The resulting
- *                               value is passed as the first parameter to addComment.moveForm(), concatenated
- *                               as $add_below-$comment->comment_ID. Default 'comment'.
- *     @type string 'respond_id' The selector identifying the responding comment. Passed as the third parameter to addComment.moveForm(),
- *                               and appended to the link URL as a hash value. Default 'respond'.
- *     @type string 'reply_text' The text of the Reply link. Default 'Reply'.
- *     @type string 'login_text' The text of the link to reply if logged out. Default 'Log in to Reply'.
- *     @type int    'depth'      The depth of the new comment. Must be greater than 0 and less than the value of the 'thread_comments_depth'
- *                               option set in Settings > Discussion.
- *                               Default 0.
- *     @type string 'before'     The text or HTML to add before the reply link. Default empty.
- *     @type string 'after'      The text or HTML to add after the reply link. Default empty.
+ *     @type string $add_below  The first part of the selector used to identify the comment to respond below.
+ *                              The resulting value is passed as the first parameter to addComment.moveForm(),
+ *                              concatenated as $add_below-$comment->comment_ID. Default 'comment'.
+ *     @type string $respond_id The selector identifying the responding comment. Passed as the third parameter
+ *                              to addComment.moveForm(), and appended to the link URL as a hash value.
+ *                              Default 'respond'.
+ *     @type string $reply_text The text of the Reply link. Default 'Reply'.
+ *     @type string $login_text The text of the link to reply if logged out. Default 'Log in to Reply'.
+ *     @type int    $depth'     The depth of the new comment. Must be greater than 0 and less than the value
+ *                              of the 'thread_comments_depth' option set in Settings > Discussion. Default 0.
+ *     @type string $before     The text or HTML to add before the reply link. Default empty.
+ *     @type string $after      The text or HTML to add after the reply link. Default empty.
  * }
- * @param int         $comment Optional. Comment being replied to. Default current comment.
- * @param int|WP_Post $post    Optional. Post ID or WP_Post object the comment is going to be displayed on. Default current post.
- * @return mixed Link to show comment form, if successful. False, if comments are closed.
+ * @param int         $comment Comment being replied to. Default current comment.
+ * @param int|WP_Post $post    Post ID or WP_Post object the comment is going to be displayed on.
+ *                             Default current post.
+ * @return null|false|string Link to show comment form, if successful. False, if comments are closed.
  */
-function get_comment_reply_link($args = array(), $comment = null, $post = null) {
+function get_comment_reply_link( $args = array(), $comment = null, $post = null ) {
 
 	$defaults = array(
-		'add_below'  => 'comment',
-		'respond_id' => 'respond',
-		'reply_text' => __('Reply'),
-		'login_text' => __('Log in to Reply'),
-		'depth'      => 0,
-		'before'     => '',
-		'after'      => ''
+		'add_below'     => 'comment',
+		'respond_id'    => 'respond',
+		'reply_text'    => __( 'Reply' ),
+		'reply_to_text' => __( 'Reply to %s' ),
+		'login_text'    => __( 'Log in to Reply' ),
+		'depth'         => 0,
+		'before'        => '',
+		'after'         => ''
 	);
 
-	$args = wp_parse_args($args, $defaults);
-
-	if ( 0 == $args['depth'] || $args['max_depth'] <= $args['depth'] )
-		return;
+	$args = wp_parse_args( $args, $defaults );
 
-	extract($args, EXTR_SKIP);
+	if ( 0 == $args['depth'] || $args['max_depth'] <= $args['depth'] ) {
+		return;
+	}
 
-	$comment = get_comment($comment);
-	if ( empty($post) )
+	$comment = get_comment( $comment );
+
+	if ( empty( $post ) ) {
 		$post = $comment->comment_post_ID;
-	$post = get_post($post);
+	}
+
+	$post = get_post( $post );
 
-	if ( !comments_open($post->ID) )
+	if ( ! comments_open( $post->ID ) ) {
 		return false;
+	}
 
-	$link = '';
+	/**
+	 * Filter the comment reply link arguments.
+	 *
+	 * @since 4.1.0
+	 *
+	 * @param array   $args    Comment reply link arguments. See {@see get_comment_reply_link()}
+	 *                         for more information on accepted arguments.
+	 * @param object  $comment The object of the comment being replied to.
+	 * @param WP_Post $post    The {@see WP_Post} object.
+	 */
+	$args = apply_filters( 'comment_reply_link_args', $args, $comment, $post );
 
-	if ( get_option('comment_registration') && ! is_user_logged_in() )
-		$link = '<a rel="nofollow" class="comment-reply-login" href="' . esc_url( wp_login_url( get_permalink() ) ) . '">' . $login_text . '</a>';
-	else
-		$link = "<a class='comment-reply-link' href='" . esc_url( add_query_arg( 'replytocom', $comment->comment_ID ) ) . "#" . $respond_id . "' onclick='return addComment.moveForm(\"$add_below-$comment->comment_ID\", \"$comment->comment_ID\", \"$respond_id\", \"$post->ID\")'>$reply_text</a>";
+	if ( get_option( 'comment_registration' ) && ! is_user_logged_in() ) {
+		$link = sprintf( '<a rel="nofollow" class="comment-reply-login" href="%s">%s</a>',
+			esc_url( wp_login_url( get_permalink() ) ),
+			$args['login_text']
+		);
+	} else {
+		$onclick = sprintf( 'return addComment.moveForm( "%1$s-%2$s", "%2$s", "%3$s", "%4$s" )',
+			$args['add_below'], $comment->comment_ID, $args['respond_id'], $post->ID
+		);
 
+		$link = sprintf( "<a class='comment-reply-link' href='%s' onclick='%s' aria-label='%s'>%s</a>",
+			esc_url( add_query_arg( 'replytocom', $comment->comment_ID ) ) . "#" . $args['respond_id'],
+			$onclick,
+			esc_attr( sprintf( $args['reply_to_text'], $comment->comment_author ) ),
+			$args['reply_text']
+		);
+	}
 	/**
 	 * Filter the comment reply link.
 	 *
 	 * @since 2.7.0
 	 *
-	 * @param string  $before  Text or HTML displayed before the reply link.
 	 * @param string  $link    The HTML markup for the comment reply link.
-	 * @param string  $after   Text or HTML displayed after the reply link.
 	 * @param array   $args    An array of arguments overriding the defaults.
 	 * @param object  $comment The object of the comment being replied.
 	 * @param WP_Post $post    The WP_Post object.
 	 */
-	return apply_filters( 'comment_reply_link', $before . $link . $after, $args, $comment, $post );
+	return apply_filters( 'comment_reply_link', $args['before'] . $link . $args['after'], $args, $comment, $post );
 }
 
 /**
@@ -1281,9 +1447,12 @@
  *
  * @since 2.7.0
  *
- * @param array       $args    Optional. Override default options, @see get_comment_reply_link()
- * @param int         $comment Optional. Comment being replied to. Default current comment.
- * @param int|WP_Post $post    Optional. Post ID or WP_Post object the comment is going to be displayed on. Default current post.
+ * @see get_comment_reply_link()
+ *
+ * @param array       $args    Optional. Override default options.
+ * @param int         $comment Comment being replied to. Default current comment.
+ * @param int|WP_Post $post    Post ID or WP_Post object the comment is going to be displayed on.
+ *                             Default current post.
  * @return mixed Link to show comment form, if successful. False, if comments are closed.
  */
 function comment_reply_link($args = array(), $comment = null, $post = null) {
@@ -1298,18 +1467,20 @@
  * @param array $args {
  *     Optional. Override default arguments.
  *
- *     @type string 'add_below'  The first part of the selector used to identify the comment to respond below.
- *                               The resulting value is passed as the first parameter to addComment.moveForm(),
- *                               concatenated as $add_below-$comment->comment_ID. Default is 'post'.
- *     @type string 'respond_id' The selector identifying the responding comment. Passed as the third parameter
- *                               to addComment.moveForm(), and appended to the link URL as a hash value. Default is 'respond'.
- *     @type string 'reply_text' The text of the Reply link. Default is 'Leave a Comment'.
- *     @type string 'login_text' The text of the link to reply if logged out. Default is 'Log in to leave a Comment'.
- *     @type string 'before'     The text or HTML to add before the reply link. Default empty.
- *     @type string 'after'      The text or HTML to add after the reply link. Default empty.
+ *     @type string $add_below  The first part of the selector used to identify the comment to respond below.
+ *                              The resulting value is passed as the first parameter to addComment.moveForm(),
+ *                              concatenated as $add_below-$comment->comment_ID. Default is 'post'.
+ *     @type string $respond_id The selector identifying the responding comment. Passed as the third parameter
+ *                              to addComment.moveForm(), and appended to the link URL as a hash value.
+ *                              Default 'respond'.
+ *     @type string $reply_text Text of the Reply link. Default is 'Leave a Comment'.
+ *     @type string $login_text Text of the link to reply if logged out. Default is 'Log in to leave a Comment'.
+ *     @type string $before     Text or HTML to add before the reply link. Default empty.
+ *     @type string $after      Text or HTML to add after the reply link. Default empty.
  * }
- * @param int|WP_Post $post    Optional. Post ID or WP_Post object the comment is going to be displayed on. Default current post.
- * @return string|bool|null Link to show comment form, if successful. False, if comments are closed.
+ * @param int|WP_Post $post    Optional. Post ID or WP_Post object the comment is going to be displayed on.
+ *                             Default current post.
+ * @return false|null|string Link to show comment form, if successful. False, if comments are closed.
  */
 function get_post_reply_link($args = array(), $post = null) {
 	$defaults = array(
@@ -1322,18 +1493,30 @@
 	);
 
 	$args = wp_parse_args($args, $defaults);
-	extract($args, EXTR_SKIP);
+
 	$post = get_post($post);
 
-	if ( !comments_open($post->ID) )
+	if ( ! comments_open( $post->ID ) ) {
 		return false;
+	}
 
-	if ( get_option('comment_registration') && ! is_user_logged_in() )
-		$link = '<a rel="nofollow" href="' . wp_login_url( get_permalink() ) . '">' . $login_text . '</a>';
-	else
-		$link = "<a rel='nofollow' class='comment-reply-link' href='" . get_permalink($post->ID) . "#$respond_id' onclick='return addComment.moveForm(\"$add_below-$post->ID\", \"0\", \"$respond_id\", \"$post->ID\")'>$reply_text</a>";
+	if ( get_option('comment_registration') && ! is_user_logged_in() ) {
+		$link = sprintf( '<a rel="nofollow" class="comment-reply-login" href="%s">%s</a>',
+			wp_login_url( get_permalink() ),
+			$args['login_text']
+		);
+	} else {
+		$onclick = sprintf( 'return addComment.moveForm( "%1$s-%2$s", "0", "%3$s", "%2$s" )',
+			$args['add_below'], $post->ID, $args['respond_id']
+		);
 
-	$formatted_link = $before . $link . $after;
+		$link = sprintf( "<a rel='nofollow' class='comment-reply-link' href='%s' onclick='%s'>%s</a>",
+			get_permalink( $post->ID ) . '#' . $args['respond_id'],
+			$onclick,
+			$args['reply_text']
+		);
+	}
+	$formatted_link = $args['before'] . $link . $args['after'];
 	/**
 	 * Filter the formatted post comments link HTML.
 	 *
@@ -1350,8 +1533,11 @@
  *
  * @since 2.7.0
  *
- * @param array       $args Optional. Override default options, @see get_post_reply_link()
- * @param int|WP_Post $post Optional. Post ID or WP_Post object the comment is going to be displayed on. Default current post.
+ * @see get_post_reply_link()
+ *
+ * @param array       $args Optional. Override default options,
+ * @param int|WP_Post $post Post ID or WP_Post object the comment is going to be displayed on.
+ *                          Default current post.
  * @return string|bool|null Link to show comment form, if successful. False, if comments are closed.
  */
 function post_reply_link($args = array(), $post = null) {
@@ -1379,8 +1565,8 @@
 	 * @since 2.7.0
 	 *
 	 * @param string $formatted_link The HTML-formatted cancel comment reply link.
-	 * @param string $link           The cancel comment reply link URL.
-	 * @param string $text           The cancel comment reply link text.
+	 * @param string $link           Cancel comment reply link URL.
+	 * @param string $text           Cancel comment reply link text.
 	 */
 	return apply_filters( 'cancel_comment_reply_link', $formatted_link, $link, $text );
 }
@@ -1438,14 +1624,17 @@
 /**
  * Display text based on comment reply status.
  *
- * Only affects users with Javascript disabled.
+ * Only affects users with JavaScript disabled.
  *
  * @since 2.7.0
  *
- * @param string $noreplytext  Optional. Text to display when not replying to a comment. Default false.
+ * @param string $noreplytext  Optional. Text to display when not replying to a comment.
+ *                             Default false.
  * @param string $replytext    Optional. Text to display when replying to a comment.
- *                             Default false. Accepts "%s" for the author of the comment being replied to.
- * @param string $linktoparent Optional. Boolean to control making the author's name a link to their comment. Default true.
+ *                             Default false. Accepts "%s" for the author of the comment
+ *                             being replied to.
+ * @param string $linktoparent Optional. Boolean to control making the author's name a link
+ *                             to their comment. Default true.
  */
 function comment_form_title( $noreplytext = false, $replytext = false, $linktoparent = true ) {
 	global $comment;
@@ -1467,7 +1656,6 @@
 /**
  * HTML comment list class.
  *
- * @package WordPress
  * @uses Walker
  * @since 2.7.0
  */
@@ -1480,7 +1668,7 @@
 	 * @since 2.7.0
 	 * @var string
 	 */
-	var $tree_type = 'comment';
+	public $tree_type = 'comment';
 
 	/**
 	 * DB fields to use.
@@ -1490,7 +1678,7 @@
 	 * @since 2.7.0
 	 * @var array
 	 */
-	var $db_fields = array ('parent' => 'comment_parent', 'id' => 'comment_ID');
+	public $db_fields = array ('parent' => 'comment_parent', 'id' => 'comment_ID');
 
 	/**
 	 * Start the list before the elements are added.
@@ -1503,18 +1691,18 @@
 	 * @param int $depth Depth of comment.
 	 * @param array $args Uses 'style' argument for type of HTML list.
 	 */
-	function start_lvl( &$output, $depth = 0, $args = array() ) {
+	public function start_lvl( &$output, $depth = 0, $args = array() ) {
 		$GLOBALS['comment_depth'] = $depth + 1;
 
 		switch ( $args['style'] ) {
 			case 'div':
 				break;
 			case 'ol':
-				echo '<ol class="children">' . "\n";
+				$output .= '<ol class="children">' . "\n";
 				break;
+			case 'ul':
 			default:
-			case 'ul':
-				echo '<ul class="children">' . "\n";
+				$output .= '<ul class="children">' . "\n";
 				break;
 		}
 	}
@@ -1530,18 +1718,18 @@
 	 * @param int    $depth  Depth of comment.
 	 * @param array  $args   Will only append content if style argument value is 'ol' or 'ul'.
 	 */
-	function end_lvl( &$output, $depth = 0, $args = array() ) {
+	public function end_lvl( &$output, $depth = 0, $args = array() ) {
 		$GLOBALS['comment_depth'] = $depth + 1;
 
 		switch ( $args['style'] ) {
 			case 'div':
 				break;
 			case 'ol':
-				echo "</ol><!-- .children -->\n";
+				$output .= "</ol><!-- .children -->\n";
 				break;
+			case 'ul':
 			default:
-			case 'ul':
-				echo "</ul><!-- .children -->\n";
+				$output .= "</ul><!-- .children -->\n";
 				break;
 		}
 	}
@@ -1566,6 +1754,7 @@
 	 *  2.2
 	 *
 	 * @see Walker::display_element()
+	 * @see wp_list_comments()
 	 *
 	 * @since 2.7.0
 	 *
@@ -1573,11 +1762,11 @@
 	 * @param array  $children_elements List of elements to continue traversing.
 	 * @param int    $max_depth         Max depth to traverse.
 	 * @param int    $depth             Depth of current element.
-	 * @param array  $args              An array of arguments. @see wp_list_comments()
+	 * @param array  $args              An array of arguments.
 	 * @param string $output            Passed by reference. Used to append additional content.
 	 * @return null Null on failure with no changes to parameters.
 	 */
-	function display_element( $element, &$children_elements, $max_depth, $depth, $args, &$output ) {
+	public function display_element( $element, &$children_elements, $max_depth, $depth, $args, &$output ) {
 
 		if ( !$element )
 			return;
@@ -1601,55 +1790,67 @@
 	/**
 	 * Start the element output.
 	 *
-	 * @see Walker::start_el()
+	 * @since 2.7.0
 	 *
-	 * @since 2.7.0
+	 * @see Walker::start_el()
+	 * @see wp_list_comments()
 	 *
 	 * @param string $output  Passed by reference. Used to append additional content.
 	 * @param object $comment Comment data object.
 	 * @param int    $depth   Depth of comment in reference to parents.
-	 * @param array  $args    An array of arguments. @see wp_list_comments()
+	 * @param array  $args    An array of arguments.
 	 */
-	function start_el( &$output, $comment, $depth = 0, $args = array(), $id = 0 ) {
+	public function start_el( &$output, $comment, $depth = 0, $args = array(), $id = 0 ) {
 		$depth++;
 		$GLOBALS['comment_depth'] = $depth;
 		$GLOBALS['comment'] = $comment;
 
 		if ( !empty( $args['callback'] ) ) {
+			ob_start();
 			call_user_func( $args['callback'], $comment, $args, $depth );
+			$output .= ob_get_clean();
 			return;
 		}
 
 		if ( ( 'pingback' == $comment->comment_type || 'trackback' == $comment->comment_type ) && $args['short_ping'] ) {
+			ob_start();
 			$this->ping( $comment, $depth, $args );
+			$output .= ob_get_clean();
 		} elseif ( 'html5' === $args['format'] ) {
+			ob_start();
 			$this->html5_comment( $comment, $depth, $args );
+			$output .= ob_get_clean();
 		} else {
+			ob_start();
 			$this->comment( $comment, $depth, $args );
+			$output .= ob_get_clean();
 		}
 	}
 
 	/**
 	 * Ends the element output, if needed.
 	 *
-	 * @see Walker::end_el()
+	 * @since 2.7.0
 	 *
-	 * @since 2.7.0
+	 * @see Walker::end_el()
+	 * @see wp_list_comments()
 	 *
 	 * @param string $output  Passed by reference. Used to append additional content.
 	 * @param object $comment The comment object. Default current comment.
 	 * @param int    $depth   Depth of comment.
-	 * @param array  $args    An array of arguments. @see wp_list_comments()
+	 * @param array  $args    An array of arguments.
 	 */
-	function end_el( &$output, $comment, $depth = 0, $args = array() ) {
+	public function end_el( &$output, $comment, $depth = 0, $args = array() ) {
 		if ( !empty( $args['end-callback'] ) ) {
+			ob_start();
 			call_user_func( $args['end-callback'], $comment, $args, $depth );
+			$output .= ob_get_clean();
 			return;
 		}
 		if ( 'div' == $args['style'] )
-			echo "</div><!-- #comment-## -->\n";
+			$output .= "</div><!-- #comment-## -->\n";
 		else
-			echo "</li><!-- #comment-## -->\n";
+			$output .= "</li><!-- #comment-## -->\n";
 	}
 
 	/**
@@ -1658,9 +1859,11 @@
 	 * @access protected
 	 * @since 3.6.0
 	 *
+	 * @see wp_list_comments()
+	 *
 	 * @param object $comment The comment object.
 	 * @param int    $depth   Depth of comment.
-	 * @param array  $args    An array of arguments. @see wp_list_comments()
+	 * @param array  $args    An array of arguments.
 	 */
 	protected function ping( $comment, $depth, $args ) {
 		$tag = ( 'div' == $args['style'] ) ? 'div' : 'li';
@@ -1678,9 +1881,11 @@
 	 * @access protected
 	 * @since 3.6.0
 	 *
+	 * @see wp_list_comments()
+	 *
 	 * @param object $comment Comment to display.
 	 * @param int    $depth   Depth of comment.
-	 * @param array  $args    An array of arguments. @see wp_list_comments()
+	 * @param array  $args    An array of arguments.
 	 */
 	protected function comment( $comment, $depth, $args ) {
 		if ( 'div' == $args['style'] ) {
@@ -1691,7 +1896,7 @@
 			$add_below = 'div-comment';
 		}
 ?>
-		<<?php echo $tag; ?> <?php comment_class( empty( $args['has_children'] ) ? '' : 'parent' ); ?> id="comment-<?php comment_ID(); ?>">
+		<<?php echo $tag; ?> <?php comment_class( $this->has_children ? 'parent' : '' ); ?> id="comment-<?php comment_ID(); ?>">
 		<?php if ( 'div' != $args['style'] ) : ?>
 		<div id="div-comment-<?php comment_ID(); ?>" class="comment-body">
 		<?php endif; ?>
@@ -1704,7 +1909,7 @@
 		<br />
 		<?php endif; ?>
 
-		<div class="comment-meta commentmetadata"><a href="<?php echo esc_url( get_comment_link( $comment->comment_ID ) ); ?>">
+		<div class="comment-meta commentmetadata"><a href="<?php echo esc_url( get_comment_link( $comment->comment_ID, $args ) ); ?>">
 			<?php
 				/* translators: 1: date, 2: time */
 				printf( __( '%1$s at %2$s' ), get_comment_date(),  get_comment_time() ); ?></a><?php edit_comment_link( __( '(Edit)' ), '&nbsp;&nbsp;', '' );
@@ -1713,9 +1918,16 @@
 
 		<?php comment_text( get_comment_id(), array_merge( $args, array( 'add_below' => $add_below, 'depth' => $depth, 'max_depth' => $args['max_depth'] ) ) ); ?>
 
-		<div class="reply">
-			<?php comment_reply_link( array_merge( $args, array( 'add_below' => $add_below, 'depth' => $depth, 'max_depth' => $args['max_depth'] ) ) ); ?>
-		</div>
+		<?php
+		comment_reply_link( array_merge( $args, array(
+			'add_below' => $add_below,
+			'depth'     => $depth,
+			'max_depth' => $args['max_depth'],
+			'before'    => '<div class="reply">',
+			'after'     => '</div>'
+		) ) );
+		?>
+
 		<?php if ( 'div' != $args['style'] ) : ?>
 		</div>
 		<?php endif; ?>
@@ -1728,14 +1940,16 @@
 	 * @access protected
 	 * @since 3.6.0
 	 *
+	 * @see wp_list_comments()
+	 *
 	 * @param object $comment Comment to display.
 	 * @param int    $depth   Depth of comment.
-	 * @param array  $args    An array of arguments. @see wp_list_comments()
+	 * @param array  $args    An array of arguments.
 	 */
 	protected function html5_comment( $comment, $depth, $args ) {
 		$tag = ( 'div' === $args['style'] ) ? 'div' : 'li';
 ?>
-		<<?php echo $tag; ?> id="comment-<?php comment_ID(); ?>" <?php comment_class( empty( $args['has_children'] ) ? '' : 'parent' ); ?>>
+		<<?php echo $tag; ?> id="comment-<?php comment_ID(); ?>" <?php comment_class( $this->has_children ? 'parent' : '' ); ?>>
 			<article id="div-comment-<?php comment_ID(); ?>" class="comment-body">
 				<footer class="comment-meta">
 					<div class="comment-author vcard">
@@ -1744,7 +1958,7 @@
 					</div><!-- .comment-author -->
 
 					<div class="comment-metadata">
-						<a href="<?php echo esc_url( get_comment_link( $comment->comment_ID ) ); ?>">
+						<a href="<?php echo esc_url( get_comment_link( $comment->comment_ID, $args ) ); ?>">
 							<time datetime="<?php comment_time( 'c' ); ?>">
 								<?php printf( _x( '%1$s at %2$s', '1: date, 2: time' ), get_comment_date(), get_comment_time() ); ?>
 							</time>
@@ -1761,9 +1975,15 @@
 					<?php comment_text(); ?>
 				</div><!-- .comment-content -->
 
-				<div class="reply">
-					<?php comment_reply_link( array_merge( $args, array( 'add_below' => 'div-comment', 'depth' => $depth, 'max_depth' => $args['max_depth'] ) ) ); ?>
-				</div><!-- .reply -->
+				<?php
+				comment_reply_link( array_merge( $args, array(
+					'add_below' => 'div-comment',
+					'depth'     => $depth,
+					'max_depth' => $args['max_depth'],
+					'before'    => '<div class="reply">',
+					'after'     => '</div>'
+				) ) );
+				?>
 			</article><!-- .comment-body -->
 <?php
 	}
@@ -1776,26 +1996,29 @@
  *
  * @since 2.7.0
  *
+ * @see WP_Query->comments
+ *
  * @param string|array $args {
  *     Optional. Formatting options.
  *
- *     @type string 'walker'            The Walker class used to list comments. Default null.
- *     @type int    'max_depth'         The maximum comments depth. Default empty.
- *     @type string 'style'             The style of list ordering. Default 'ul'. Accepts 'ul', 'ol'.
- *     @type string 'callback'          Callback function to use. Default null.
- *     @type string 'end-callback'      Callback function to use at the end. Default null.
- *     @type string 'type'              Type of comments to list.
- *                                      Default 'all'. Accepts 'all', 'comment', 'pingback', 'trackback', 'pings'.
- *     @type int    'page'              Page ID to list comments for. Default empty.
- *     @type int    'per_page'          Number of comments to list per page. Default empty.
- *     @type int    'avatar_size'       Height and width dimensions of the avatar size. Default 32.
- *     @type string 'reverse_top_level' Ordering of the listed comments. Default null. Accepts 'desc', 'asc'.
- *     @type bool   'reverse_children'  Whether to reverse child comments in the list. Default null.
- *     @type string 'format'            How to format the comments list.
- *                                      Default 'html5' if the theme supports it. Accepts 'html5', 'xhtml'.
- *     @type bool   'short_ping'        Whether to output short pings. Default false.
+ *     @type object $walker            Instance of a Walker class to list comments. Default null.
+ *     @type int    $max_depth         The maximum comments depth. Default empty.
+ *     @type string $style             The style of list ordering. Default 'ul'. Accepts 'ul', 'ol'.
+ *     @type string $callback          Callback function to use. Default null.
+ *     @type string $end-callback      Callback function to use at the end. Default null.
+ *     @type string $type              Type of comments to list.
+ *                                     Default 'all'. Accepts 'all', 'comment', 'pingback', 'trackback', 'pings'.
+ *     @type int    $page              Page ID to list comments for. Default empty.
+ *     @type int    $per_page          Number of comments to list per page. Default empty.
+ *     @type int    $avatar_size       Height and width dimensions of the avatar size. Default 32.
+ *     @type string $reverse_top_level Ordering of the listed comments. Default null. Accepts 'desc', 'asc'.
+ *     @type bool   $reverse_children  Whether to reverse child comments in the list. Default null.
+ *     @type string $format            How to format the comments list.
+ *                                     Default 'html5' if the theme supports it. Accepts 'html5', 'xhtml'.
+ *     @type bool   $short_ping        Whether to output short pings. Default false.
+ *     @type bool   $echo              Whether to echo the output or return it. Default true.
  * }
- * @param array $comments Optional. Array of comment objects. @see WP_Query->comments
+ * @param array $comments Optional. Array of comment objects.
  */
 function wp_list_comments( $args = array(), $comments = null ) {
 	global $wp_query, $comment_alt, $comment_depth, $comment_thread_alt, $overridden_cpage, $in_comment_loop;
@@ -1819,10 +2042,22 @@
 		'reverse_children'  => '',
 		'format'            => current_theme_supports( 'html5', 'comment-list' ) ? 'html5' : 'xhtml',
 		'short_ping'        => false,
+		'echo'              => true,
 	);
 
 	$r = wp_parse_args( $args, $defaults );
 
+	/**
+	 * Filter the arguments used in retrieving the comment list.
+	 *
+	 * @since 4.0.0
+	 *
+	 * @see wp_list_comments()
+	 *
+	 * @param array $r An array of arguments for displaying comments.
+	 */
+	$r = apply_filters( 'wp_list_comments_args', $r );
+
 	// Figure out what comments we'll be looping through ($_comments)
 	if ( null !== $comments ) {
 		$comments = (array) $comments;
@@ -1882,15 +2117,22 @@
 	if ( null === $r['reverse_top_level'] )
 		$r['reverse_top_level'] = ( 'desc' == get_option('comment_order') );
 
-	extract( $r, EXTR_SKIP );
+	if ( empty( $r['walker'] ) ) {
+		$walker = new Walker_Comment;
+	} else {
+		$walker = $r['walker'];
+	}
 
-	if ( empty($walker) )
-		$walker = new Walker_Comment;
-
-	$walker->paged_walk($_comments, $max_depth, $page, $per_page, $r);
+	$output = $walker->paged_walk( $_comments, $r['max_depth'], $r['page'], $r['per_page'], $r );
 	$wp_query->max_num_comment_pages = $walker->max_pages;
 
 	$in_comment_loop = false;
+
+	if ( $r['echo'] ) {
+		echo $output;
+	} else {
+		return $output;
+	}
 }
 
 /**
@@ -1904,40 +2146,47 @@
  * in the array of fields.
  *
  * @since 3.0.0
+ * @since 4.1.0 Introduced the 'class_submit' argument.
+ * @since 4.2.0 Introduced 'submit_button' and 'submit_fields' arguments.
  *
  * @param array       $args {
  *     Optional. Default arguments and form fields to override.
  *
- *     @type array 'fields' {
+ *     @type array $fields {
  *         Default comment fields, filterable by default via the 'comment_form_default_fields' hook.
  *
- *         @type string 'author' The comment author field HTML.
- *         @type string 'email'  The comment author email field HTML.
- *         @type string 'url'    The comment author URL field HTML.
+ *         @type string $author Comment author field HTML.
+ *         @type string $email  Comment author email field HTML.
+ *         @type string $url    Comment author URL field HTML.
  *     }
- *     @type string 'comment_field'        The comment textarea field HTML.
- *     @type string 'must_log_in'          HTML element for a 'must be logged in to comment' message.
- *     @type string 'logged_in_as'         HTML element for a 'logged in as <user>' message.
- *     @type string 'comment_notes_before' HTML element for a message displayed before the comment form.
- *                                         Default 'Your email address will not be published.'.
- *     @type string 'comment_notes_after'  HTML element for a message displayed after the comment form.
- *                                         Default 'You may use these HTML tags and attributes ...'.
- *     @type string 'id_form'              The comment form element id attribute. Default 'commentform'.
- *     @type string 'id_submit'            The comment submit element id attribute. Default 'submit'.
- *     @type string 'title_reply'          The translatable 'reply' button label. Default 'Leave a Reply'.
- *     @type string 'title_reply_to'       The translatable 'reply-to' button label. Default 'Leave a Reply to %s',
- *                                         where %s is the author of the comment being replied to.
- *     @type string 'cancel_reply_link'    The translatable 'cancel reply' button label. Default 'Cancel reply'.
- *     @type string 'label_submit'         The translatable 'submit' button label. Default 'Post a comment'.
- *     @type string 'format'               The comment form format. Default 'xhtml'. Accepts 'xhtml', 'html5'.
+ *     @type string $comment_field        The comment textarea field HTML.
+ *     @type string $must_log_in          HTML element for a 'must be logged in to comment' message.
+ *     @type string $logged_in_as         HTML element for a 'logged in as [user]' message.
+ *     @type string $comment_notes_before HTML element for a message displayed before the comment form.
+ *                                        Default 'Your email address will not be published.'.
+ *     @type string $comment_notes_after  HTML element for a message displayed after the comment form.
+ *                                        Default 'You may use these HTML tags and attributes ...'.
+ *     @type string $id_form              The comment form element id attribute. Default 'commentform'.
+ *     @type string $id_submit            The comment submit element id attribute. Default 'submit'.
+ *     @type string $class_submit         The comment submit element class attribute. Default 'submit'.
+ *     @type string $name_submit          The comment submit element name attribute. Default 'submit'.
+ *     @type string $title_reply          The translatable 'reply' button label. Default 'Leave a Reply'.
+ *     @type string $title_reply_to       The translatable 'reply-to' button label. Default 'Leave a Reply to %s',
+ *                                        where %s is the author of the comment being replied to.
+ *     @type string $cancel_reply_link    The translatable 'cancel reply' button label. Default 'Cancel reply'.
+ *     @type string $label_submit         The translatable 'submit' button label. Default 'Post a comment'.
+ *     @type string $submit_button        HTML format for the Submit button.
+ *                                        Default: '<input name="%1$s" type="submit" id="%2$s" class="%3$s" value="%4$s" />'.
+ *     @type string $submit_field         HTML format for the markup surrounding the Submit button and comment hidden
+ *                                        fields. Default: '<p class="form-submit">%1$s %2$s</a>', where %1$s is the
+ *                                        submit button markup and %2$s is the comment hidden fields.
+ *     @type string $format               The comment form format. Default 'xhtml'. Accepts 'xhtml', 'html5'.
  * }
- * @param int|WP_Post $post_id Optional. Post ID or WP_Post object to generate the form for. Default current post.
+ * @param int|WP_Post $post_id Post ID or WP_Post object to generate the form for. Default current post.
  */
 function comment_form( $args = array(), $post_id = null ) {
 	if ( null === $post_id )
 		$post_id = get_the_ID();
-	else
-		$id = $post_id;
 
 	$commenter = wp_get_current_commenter();
 	$user = wp_get_current_user();
@@ -1949,12 +2198,13 @@
 
 	$req      = get_option( 'require_name_email' );
 	$aria_req = ( $req ? " aria-required='true'" : '' );
+	$html_req = ( $req ? " required='required'" : '' );
 	$html5    = 'html5' === $args['format'];
 	$fields   =  array(
 		'author' => '<p class="comment-form-author">' . '<label for="author">' . __( 'Name' ) . ( $req ? ' <span class="required">*</span>' : '' ) . '</label> ' .
-		            '<input id="author" name="author" type="text" value="' . esc_attr( $commenter['comment_author'] ) . '" size="30"' . $aria_req . ' /></p>',
+		            '<input id="author" name="author" type="text" value="' . esc_attr( $commenter['comment_author'] ) . '" size="30"' . $aria_req . $html_req . ' /></p>',
 		'email'  => '<p class="comment-form-email"><label for="email">' . __( 'Email' ) . ( $req ? ' <span class="required">*</span>' : '' ) . '</label> ' .
-		            '<input id="email" name="email" ' . ( $html5 ? 'type="email"' : 'type="text"' ) . ' value="' . esc_attr(  $commenter['comment_author_email'] ) . '" size="30"' . $aria_req . ' /></p>',
+		            '<input id="email" name="email" ' . ( $html5 ? 'type="email"' : 'type="text"' ) . ' value="' . esc_attr(  $commenter['comment_author_email'] ) . '" size="30" aria-describedby="email-notes"' . $aria_req . $html_req  . ' /></p>',
 		'url'    => '<p class="comment-form-url"><label for="url">' . __( 'Website' ) . '</label> ' .
 		            '<input id="url" name="url" ' . ( $html5 ? 'type="url"' : 'type="text"' ) . ' value="' . esc_attr( $commenter['comment_author_url'] ) . '" size="30" /></p>',
 	);
@@ -1971,17 +2221,23 @@
 	$fields = apply_filters( 'comment_form_default_fields', $fields );
 	$defaults = array(
 		'fields'               => $fields,
-		'comment_field'        => '<p class="comment-form-comment"><label for="comment">' . _x( 'Comment', 'noun' ) . '</label> <textarea id="comment" name="comment" cols="45" rows="8" aria-required="true"></textarea></p>',
+		'comment_field'        => '<p class="comment-form-comment"><label for="comment">' . _x( 'Comment', 'noun' ) . '</label> <textarea id="comment" name="comment" cols="45" rows="8" aria-describedby="form-allowed-tags" aria-required="true" required="required"></textarea></p>',
+		/** This filter is documented in wp-includes/link-template.php */
 		'must_log_in'          => '<p class="must-log-in">' . sprintf( __( 'You must be <a href="%s">logged in</a> to post a comment.' ), wp_login_url( apply_filters( 'the_permalink', get_permalink( $post_id ) ) ) ) . '</p>',
+		/** This filter is documented in wp-includes/link-template.php */
 		'logged_in_as'         => '<p class="logged-in-as">' . sprintf( __( 'Logged in as <a href="%1$s">%2$s</a>. <a href="%3$s" title="Log out of this account">Log out?</a>' ), get_edit_user_link(), $user_identity, wp_logout_url( apply_filters( 'the_permalink', get_permalink( $post_id ) ) ) ) . '</p>',
-		'comment_notes_before' => '<p class="comment-notes">' . __( 'Your email address will not be published.' ) . ( $req ? $required_text : '' ) . '</p>',
-		'comment_notes_after'  => '<p class="form-allowed-tags">' . sprintf( __( 'You may use these <abbr title="HyperText Markup Language">HTML</abbr> tags and attributes: %s' ), ' <code>' . allowed_tags() . '</code>' ) . '</p>',
+		'comment_notes_before' => '<p class="comment-notes"><span id="email-notes">' . __( 'Your email address will not be published.' ) . '</span>'. ( $req ? $required_text : '' ) . '</p>',
+		'comment_notes_after'  => '<p class="form-allowed-tags" id="form-allowed-tags">' . sprintf( __( 'You may use these <abbr title="HyperText Markup Language">HTML</abbr> tags and attributes: %s' ), ' <code>' . allowed_tags() . '</code>' ) . '</p>',
 		'id_form'              => 'commentform',
 		'id_submit'            => 'submit',
+		'class_submit'         => 'submit',
+		'name_submit'          => 'submit',
 		'title_reply'          => __( 'Leave a Reply' ),
 		'title_reply_to'       => __( 'Leave a Reply to %s' ),
 		'cancel_reply_link'    => __( 'Cancel reply' ),
 		'label_submit'         => __( 'Post Comment' ),
+		'submit_button'        => '<input name="%1$s" type="submit" id="%2$s" class="%3$s" value="%4$s" />',
+		'submit_field'         => '<p class="form-submit">%1$s %2$s</p>',
 		'format'               => 'xhtml',
 	);
 
@@ -1996,8 +2252,7 @@
 	 */
 	$args = wp_parse_args( $args, apply_filters( 'comment_form_defaults', $defaults ) );
 
-	?>
-		<?php if ( comments_open( $post_id ) ) : ?>
+		if ( comments_open( $post_id ) ) : ?>
 			<?php
 			/**
 			 * Fires before the comment form.
@@ -2022,7 +2277,7 @@
 					<form action="<?php echo site_url( '/wp-comments-post.php' ); ?>" method="post" id="<?php echo esc_attr( $args['id_form'] ); ?>" class="comment-form"<?php echo $html5 ? ' novalidate' : ''; ?>>
 						<?php
 						/**
-						 * Fires at the top of the comment form, inside the <form> tag.
+						 * Fires at the top of the comment form, inside the form tag.
 						 *
 						 * @since 3.0.0
 						 */
@@ -2035,9 +2290,11 @@
 							 *
 							 * @since 3.0.0
 							 *
-							 * @param string $args['logged_in_as'] The logged-in-as HTML-formatted message.
-							 * @param array  $commenter            An array containing the comment author's username, email, and URL.
-							 * @param string $user_identity        If the commenter is a registered user, the display name, blank otherwise.
+							 * @param string $args_logged_in The logged-in-as HTML-formatted message.
+							 * @param array  $commenter      An array containing the comment author's
+							 *                               username, email, and URL.
+							 * @param string $user_identity  If the commenter is a registered user,
+							 *                               the display name, blank otherwise.
 							 */
 							echo apply_filters( 'comment_form_logged_in', $args['logged_in_as'], $commenter, $user_identity );
 							?>
@@ -2047,8 +2304,10 @@
 							 *
 							 * @since 3.0.0
 							 *
-							 * @param array  $commenter     An array containing the comment author's username, email, and URL.
-							 * @param string $user_identity If the commenter is a registered user, the display name, blank otherwise.
+							 * @param array  $commenter     An array containing the comment author's
+							 *                              username, email, and URL.
+							 * @param string $user_identity If the commenter is a registered user,
+							 *                              the display name, blank otherwise.
 							 */
 							do_action( 'comment_form_logged_in_after', $commenter, $user_identity );
 							?>
@@ -2065,7 +2324,7 @@
 								/**
 								 * Filter a comment form field for display.
 								 *
-								 * The dynamic portion of the filter hook, $name, refers to the name
+								 * The dynamic portion of the filter hook, `$name`, refers to the name
 								 * of the comment form field. Such as 'author', 'email', or 'url'.
 								 *
 								 * @since 3.0.0
@@ -2088,20 +2347,54 @@
 						 *
 						 * @since 3.0.0
 						 *
-						 * @param string $args['comment_field'] The content of the comment textarea field.
+						 * @param string $args_comment_field The content of the comment textarea field.
 						 */
 						echo apply_filters( 'comment_form_field_comment', $args['comment_field'] );
 						?>
 						<?php echo $args['comment_notes_after']; ?>
-						<p class="form-submit">
-							<input name="submit" type="submit" id="<?php echo esc_attr( $args['id_submit'] ); ?>" value="<?php echo esc_attr( $args['label_submit'] ); ?>" />
-							<?php comment_id_fields( $post_id ); ?>
-						</p>
+
 						<?php
+						$submit_button = sprintf(
+							$args['submit_button'],
+							esc_attr( $args['name_submit'] ),
+							esc_attr( $args['id_submit'] ),
+							esc_attr( $args['class_submit'] ),
+							esc_attr( $args['label_submit'] )
+						);
+
+						/**
+						 * Filter the submit button for the comment form to display.
+						 *
+						 * @since 4.2.0
+						 *
+						 * @param string $submit_button HTML markup for the submit button.
+						 * @param array  $args          Arguments passed to `comment_form()`.
+						 */
+						$submit_button = apply_filters( 'comment_form_submit_button', $submit_button, $args );
+
+						$submit_field = sprintf(
+							$args['submit_field'],
+							$submit_button,
+							get_comment_id_fields( $post_id )
+						);
+
+						/**
+						 * Filter the submit field for the comment form to display.
+						 *
+						 * The submit field includes the submit button, hidden fields for the
+						 * comment form, and any wrapper markup.
+						 *
+						 * @since 4.2.0
+						 *
+						 * @param string $submit_field HTML markup for the submit field.
+						 * @param array  $args         Arguments passed to comment_form().
+						 */
+						echo apply_filters( 'comment_form_submit_field', $submit_field, $args );
+
 						/**
 						 * Fires at the bottom of the comment form, inside the closing </form> tag.
 						 *
-						 * @since 1.5.2
+						 * @since 1.5.0
 						 *
 						 * @param int $post_id The post ID.
 						 */