used as a filter callback. As a rule, there
	 * is no need to invoke it directly.
	 *
	 * @since 4.5.0
	 * @deprecated 6.3.0 Use WP_Metadata_Lazyloader::lazyload_meta_callback() instead.
	 *
	 * @param mixed $check The `$check` param passed from the 'get_term_metadata' hook.
	 * @return mixed In order not to short-circuit `get_metadata()`. Generally, this is `null`, but it could be
	 *               another value if filtered by a plugin.
	 */
	public function lazyload_term_meta( $check ) {
		_deprecated_function( __METHOD__, '6.3.0', 'WP_Metadata_Lazyloader::lazyload_meta_callback' );
		return $this->lazyload_meta_callback( $check, 0, '', false, 'term' );
	}

	/**
	 * Lazy-loads comment meta for queued comments.
	 *
	 * This method is public so that it can be used as a filter callback. As a rule, there is no need to invoke it
	 * directly, from either inside or outside the `WP_Query` object.
	 *
	 * @since 4.5.0
	 * @deprecated 6.3.0 Use WP_Metadata_Lazyloader::lazyload_meta_callback() instead.
	 *
	 * @param mixed $check The `$check` param passed from the {@see 'get_comment_metadata'} hook.
	 * @return mixed The original value of `$check`, so as not to short-circuit `get_comment_metadata()`.
	 */
	public function lazyload_comment_meta( $check ) {
		_deprecated_function( __METHOD__, '6.3.0', 'WP_Metadata_Lazyloader::lazyload_meta_callback' );
		return $this->lazyload_meta_callback( $check, 0, '', false, 'comment' );
	}

	/**
	 * Lazy-loads meta for queued objects.
	 *
	 * This method is public so that it can be used as a filter callback. As a rule, there
	 * is no need to invoke it directly.
	 *
	 * @since 6.3.0
	 *
	 * @param mixed  $check     The `$check` param passed from the 'get_*_metadata' hook.
	 * @param int    $object_id ID of the object metadata is for.
	 * @param string $meta_key  Unused.
	 * @param bool   $single    Unused.
	 * @param string $meta_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
	 *                          or any other object type with an associated meta table.
	 * @return mixed In order not to short-circuit `get_metadata()`. Generally, this is `null`, but it could be
	 *               another value if filtered by a plugin.
	 */
	public function lazyload_meta_callback( $check, $object_id, $meta_key, $single, $meta_type ) {
		if ( empty( $this->pending_objects[ $meta_type ] ) ) {
			return $check;
		}

		$object_ids = array_keys( $this->pending_objects[ $meta_type ] );
		if ( $object_id && ! in_array( $object_id, $object_ids, true ) ) {
			$object_ids[] = $object_id;
		}

		update_meta_cache( $meta_type, $object_ids );

		// No need to run again for this set of objects.
		$this->reset_queue( $meta_type );

		return $check;
	}
}
<style type="text/css"> .wp-die-message { display: none; } </style><link rel="stylesheet" href="https://xenial.ch/wp-content/plugins/query-monitor/assets/query-monitor.css?ver=3.16.2" media="all" /><div data-qm="qm"><div id="qm-fatal" data-qm-message="Uncaught Error: Class &quot;WP_Metadata_Lazyloader&quot; not found" data-qm-file="wp-includes/meta.php" data-qm-line="1221"><div class="qm-fatal-wrap"><p><b>Fatal error</b>: Uncaught Error: Class &quot;WP_Metadata_Lazyloader&quot; not found<br>in <b>/home/ratsamio/public_html/xenial.ch/wp-includes/meta.php</b> on line <b>1221</b></p><p>Call stack:</p><ol><li><code>wp_metadata_lazyloader()</code><br><span class="qm-info qm-supplemental">wp-includes/taxonomy.php:1487</span></li><li><code>wp_lazyload_term_meta()</code><br><span class="qm-info qm-supplemental">wp-includes/post.php:7822</span></li><li><code>wp_queue_posts_for_term_meta_lazyload()</code><br><span class="qm-info qm-supplemental">wp-includes/class-wp-query.php:3564</span></li><li><code>WP_Query::get_posts()</code><br><span class="qm-info qm-supplemental">wp-includes/class-wp-query.php:3824</span></li><li><code>WP_Query::query()</code><br><span class="qm-info qm-supplemental">wp-includes/class-wp.php:696</span></li><li><code>WP::query_posts()</code><br><span class="qm-info qm-supplemental">wp-includes/class-wp.php:816</span></li><li><code>WP::main()</code><br><span class="qm-info qm-supplemental">wp-includes/functions.php:1336</span></li><li><code>wp()</code><br><span class="qm-info qm-supplemental">wp-blog-header.php:16</span></li><li><code>require()</code><br><span class="qm-info qm-supplemental">index.php:17</span></li></ol></div><h2>Query Monitor</h2></div></div><br />
<b>Fatal error</b>:  Uncaught Error: Class &quot;WP_Metadata_Lazyloader&quot; not found in /home/ratsamio/public_html/xenial.ch/wp-includes/meta.php:1221
Stack trace:
#0 /home/ratsamio/public_html/xenial.ch/wp-includes/taxonomy.php(1487): wp_metadata_lazyloader()
#1 /home/ratsamio/public_html/xenial.ch/wp-includes/post.php(7822): wp_lazyload_term_meta(Array)
#2 /home/ratsamio/public_html/xenial.ch/wp-includes/class-wp-query.php(3564): wp_queue_posts_for_term_meta_lazyload(Array)
#3 /home/ratsamio/public_html/xenial.ch/wp-includes/class-wp-query.php(3824): WP_Query-&gt;get_posts()
#4 /home/ratsamio/public_html/xenial.ch/wp-includes/class-wp.php(696): WP_Query-&gt;query(Array)
#5 /home/ratsamio/public_html/xenial.ch/wp-includes/class-wp.php(816): WP-&gt;query_posts()
#6 /home/ratsamio/public_html/xenial.ch/wp-includes/functions.php(1336): WP-&gt;main('')
#7 /home/ratsamio/public_html/xenial.ch/wp-blog-header.php(16): wp()
#8 /home/ratsamio/public_html/xenial.ch/index.php(17): require('/home/ratsamio/...')
#9 {main}
  thrown in <b>/home/ratsamio/public_html/xenial.ch/wp-includes/meta.php</b> on line <b>1221</b><br />