WordPress/wp-includes/feed-atom-comments.php

<?php
/**
 * Atom Feed Template for displaying Atom Comments feed.
 *
 * @package WordPress
 */

header( 'Content-Type: ' . feed_content_type( 'atom' ) . '; charset=' . get_option( 'blog_charset' ), true );
echo '<?xml version="1.0" encoding="' . get_option( 'blog_charset' ) . '" ?' . '>';

/** This action is documented in wp-includes/feed-rss2.php */
do_action( 'rss_tag_pre', 'atom-comments' );
?>
<feed
	xmlns="http://www.w3.org/2005/Atom"
	xml:lang="<?php bloginfo_rss( 'language' ); ?>"
	xmlns:thr="http://purl.org/syndication/thread/1.0"
	<?php
		/** This action is documented in wp-includes/feed-atom.php */
		do_action( 'atom_ns' );

		/**
		 * Fires inside the feed tag in the Atom comment feed.
		 *
		 * @since 2.8.0
		 */
		do_action( 'atom_comments_ns' );
	?>
>
	<title type="text">
	<?php
	if ( is_singular() ) {
		/* translators: Comments feed title. %s: Post title */
		printf( ent2ncr( __( 'Comments on %s' ) ), get_the_title_rss() );
	} elseif ( is_search() ) {
		/* translators: Comments feed title. 1: Site name, 2: Search query */
		printf( ent2ncr( __( 'Comments for %1$s searching on %2$s' ) ), get_bloginfo_rss( 'name' ), get_search_query() );
	} else {
		/* translators: Comments feed title. %s: Site name */
		printf( ent2ncr( __( 'Comments for %s' ) ), get_wp_title_rss() );
	}
	?>
	</title>
	<subtitle type="text"><?php bloginfo_rss( 'description' ); ?></subtitle>

	<updated><?php // phpcs:ignore Squiz.PHP.EmbeddedPhp.ContentBeforeOpen,Squiz.PHP.EmbeddedPhp.ContentAfterOpen
		$date = get_last_build_date();
		echo $date ? mysql2date( 'Y-m-d\TH:i:s\Z', $date, false ) : date( 'Y-m-d\TH:i:s\Z' );
		// phpcs:ignore Squiz.PHP.EmbeddedPhp.ContentAfterEnd
	?></updated>

<?php if ( is_singular() ) { ?>
	<link rel="alternate" type="<?php bloginfo_rss( 'html_type' ); ?>" href="<?php comments_link_feed(); ?>" />
	<link rel="self" type="application/atom+xml" href="<?php echo esc_url( get_post_comments_feed_link( '', 'atom' ) ); ?>" />
	<id><?php echo esc_url( get_post_comments_feed_link( '', 'atom' ) ); ?></id>
<?php } elseif ( is_search() ) { ?>
	<link rel="alternate" type="<?php bloginfo_rss( 'html_type' ); ?>" href="<?php echo home_url() . '?s=' . get_search_query(); ?>" />
	<link rel="self" type="application/atom+xml" href="<?php echo get_search_comments_feed_link( '', 'atom' ); ?>" />
	<id><?php echo get_search_comments_feed_link( '', 'atom' ); ?></id>
<?php } else { ?>
	<link rel="alternate" type="<?php bloginfo_rss( 'html_type' ); ?>" href="<?php bloginfo_rss( 'url' ); ?>" />
	<link rel="self" type="application/atom+xml" href="<?php bloginfo_rss( 'comments_atom_url' ); ?>" />
	<id><?php bloginfo_rss( 'comments_atom_url' ); ?></id>
<?php } ?>
<?php
	/**
	 * Fires at the end of the Atom comment feed header.
	 *
	 * @since 2.8.0
	 */
	do_action( 'comments_atom_head' );
?>
<?php
if ( have_comments() ) :
	while ( have_comments() ) :
		the_comment();
		$comment_post = $GLOBALS['post'] = get_post( $comment->comment_post_ID );
		?>
	<entry>
		<title>
		<?php
		if ( ! is_singular() ) {
			$title = get_the_title( $comment_post->ID );
			/** This filter is documented in wp-includes/feed.php */
			$title = apply_filters( 'the_title_rss', $title );
			/* translators: Individual comment title. 1: Post title, 2: Comment author name */
			printf( ent2ncr( __( 'Comment on %1$s by %2$s' ) ), $title, get_comment_author_rss() );
		} else {
			/* translators: Comment author title. %s: Comment author name */
			printf( ent2ncr( __( 'By: %s' ) ), get_comment_author_rss() );
		}
		?>
			</title>
			<link rel="alternate" href="<?php comment_link(); ?>" type="<?php bloginfo_rss( 'html_type' ); ?>" />

		<author>
			<name><?php comment_author_rss(); ?></name>
			<?php
			if ( get_comment_author_url() ) {
				echo '<uri>' . get_comment_author_url() . '</uri>';}
			?>

		</author>

		<id><?php comment_guid(); ?></id>
		<updated><?php echo mysql2date( 'Y-m-d\TH:i:s\Z', get_comment_time( 'Y-m-d H:i:s', true, false ), false ); ?></updated>
		<published><?php echo mysql2date( 'Y-m-d\TH:i:s\Z', get_comment_time( 'Y-m-d H:i:s', true, false ), false ); ?></published>
		<?php if ( post_password_required( $comment_post ) ) : ?>
		<content type="html" xml:base="<?php comment_link(); ?>"><![CDATA[<?php echo get_the_password_form(); ?>]]></content>
	<?php else : // post pass ?>
		<content type="html" xml:base="<?php comment_link(); ?>"><![CDATA[<?php comment_text(); ?>]]></content>
		<?php
	endif; // post pass
	// Return comment threading information (https://www.ietf.org/rfc/rfc4685.txt)
	if ( $comment->comment_parent == 0 ) : // This comment is top level
		?>
	<thr:in-reply-to ref="<?php the_guid(); ?>" href="<?php the_permalink_rss(); ?>" type="<?php bloginfo_rss( 'html_type' ); ?>" />
		<?php
	else : // This comment is in reply to another comment
		$parent_comment = get_comment( $comment->comment_parent );
		// The rel attribute below and the id tag above should be GUIDs, but WP doesn't create them for comments (unlike posts). Either way, it's more important that they both use the same system
		?>
		<thr:in-reply-to ref="<?php comment_guid( $parent_comment ); ?>" href="<?php echo get_comment_link( $parent_comment ); ?>" type="<?php bloginfo_rss( 'html_type' ); ?>" />
		<?php
endif;
	/**
	 * Fires at the end of each Atom comment feed item.
	 *
	 * @since 2.2.0
	 *
	 * @param int $comment_id      ID of the current comment.
	 * @param int $comment_post_id ID of the post the current comment is connected to.
	 */
	do_action( 'comment_atom_entry', $comment->comment_ID, $comment_post->ID );
	?>
	</entry>
		<?php
	endwhile;
endif;
?>
</feed>