Creates an HTML list of threaded comments.

Since: 2.7.0
Source: wp-includes/class-walker-comment.php
Used by: wp_list_comments()

Class Synopsis

class Walker_Comment extends Walker {
    public $tree_type = 'comment';
    public $db_fields = [
        'parent' => 'comment_parent',
        'id'     => 'comment_ID',
    ];
    
    public function start_lvl( &$output, $depth = 0, $args = [] );
    public function end_lvl( &$output, $depth = 0, $args = [] );
    public function start_el( &$output, $data_object, $depth = 0, $args = [], $current_object_id = 0 );
    public function end_el( &$output, $data_object, $depth = 0, $args = [] );
    
    // Override for orphan handling
    public function display_element( $element, &$children_elements, $max_depth, $depth, $args, &$output );
    
    // Output methods
    protected function ping( $comment, $depth, $args );
    protected function comment( $comment, $depth, $args );
    protected function html5_comment( $comment, $depth, $args );
    
    // Filter method
    public function filter_comment_text( $comment_text, $comment ): string;
}

Configuration

$db_fields

public $db_fields = [
    'parent' => 'comment_parent',  // WP_Comment->comment_parent
    'id'     => 'comment_ID',      // WP_Comment->comment_ID
];

Methods

start_lvl()

Opens a child comment container. Sets global $comment_depth.

public function start_lvl( &$output, $depth = 0, $args = [] )

Output by style:

• div: Nothing (divs don’t need container)
• ol: <ol class="children">
• ul (default): <ul class="children">

end_lvl()

Closes the child comment container.

public function end_lvl( &$output, $depth = 0, $args = [] )

Output:

</ul><!-- .children -->

start_el()

Outputs a comment. Delegates to rendering methods based on type and format.

public function start_el( &$output, $data_object, $depth = 0, $args = [], $current_object_id = 0 )

Sets globals:

• $comment_depth — Current nesting depth
• $comment — Current comment object

Rendering decision tree:

1. If $args['callback'] is set → Call custom callback
2. If pingback/trackback and $args['short_ping'] → Call ping()
3. If $args['format'] === 'html5' → Call html5_comment()
4. Otherwise → Call comment()

end_el()

Closes the comment element.

public function end_el( &$output, $data_object, $depth = 0, $args = [] )

Uses $args['end-callback'] if set, otherwise:

• div style: </div><!-- #comment-## -->
• List style: </li><!-- #comment-## -->

display_element()

Override of parent method to handle deeply nested orphans.

public function display_element( $element, &$children_elements, $max_depth, $depth, $args, &$output )

Special behavior: When at max depth with remaining children, displays them inline at the current depth instead of orphaning them at the end.

Example with max_depth = 2:

Comment 1
  └── Reply 1.1
      Reply 1.1.1 (displayed here, not orphaned)
      Reply 1.1.2

Rendering Methods

ping()

Outputs a pingback/trackback in short format.

protected function ping( $comment, $depth, $args )

Output:

<li id="comment-123" class="pingback">
    <div class="comment-body">
        Pingback: <a href="...">Source Site</a> <span class="edit-link"><a href="...">Edit</a></span>
    </div>

comment()

Outputs a standard comment (XHTML format).

protected function comment( $comment, $depth, $args )

Structure:

<li class="comment parent" id="comment-123">
    <div id="div-comment-123" class="comment-body">
        <div class="comment-author vcard">
            <img class="avatar" ... />
            <cite class="fn"><a href="...">Author Name</a></cite> <span class="says">says:</span>
        </div>
        <div class="comment-meta commentmetadata">
            <a href="#comment-123">January 1, 2024 at 12:00 pm</a>
            <a href="...">(Edit)</a>
        </div>
        <p>Comment text...</p>
        <div class="reply">
            <a href="?replytocom=123">Reply</a>
        </div>
    </div>

html5_comment()

Outputs a comment in HTML5 format.

protected function html5_comment( $comment, $depth, $args )

Structure:

<li id="comment-123" class="comment parent">
    <article id="div-comment-123" class="comment-body">
        <footer class="comment-meta">
            <div class="comment-author vcard">
                <img class="avatar" ... />
                <b class="fn">Author Name</b> <span class="says">says:</span>
            </div>
            <div class="comment-metadata">
                <a href="#comment-123"><time datetime="2024-01-01T12:00:00+00:00">January 1, 2024 at 12:00 pm</time></a>
            </div>
        </footer>
        <div class="comment-content">
            <p>Comment text...</p>
        </div>
        <div class="reply">
            <a href="?replytocom=123">Reply</a>
        </div>
    </article>

Filter Method

filter_comment_text()

Since: 5.4.2

Removes links from pending comments if the commenter didn’t consent to cookies.

public function filter_comment_text( $comment_text, $comment ): string

Applied via add_filter( 'comment_text', ... ) during regular comment output.

Args Reference

Usage Example

// Direct usage
$walker = new Walker_Comment();
$comments = get_comments( [ 'post_id' => get_the_ID() ] );

echo '<ol class="comment-list">';
echo $walker->paged_walk(
    $comments,
    get_option( 'thread_comments_depth' ),
    get_query_var( 'cpage' ) ?: 1,
    get_option( 'comments_per_page' ),
    [
        'style'       => 'ol',
        'format'      => 'html5',
        'avatar_size' => 48,
    ]
);
echo '</ol>';

// Via wp_list_comments() with custom callback
wp_list_comments( [
    'callback' => function( $comment, $args, $depth ) {
        echo '<li>';
        echo '<strong>' . get_comment_author() . '</strong>';
        echo get_comment_text();
    },
    'end-callback' => function() {
        echo '</li>';
    },
] );

CSS Classes

Applied to comment elements:

Related

• wp_list_comments() — Main function using this walker
• get_comment_class() — CSS class generation
• comment_text filter — Modify comment content