1<?php
  2/**
  3 * Appending the wp-block-heading to before rendering the stored `core/heading` block contents.
  4 *
  5 * @package WordPress
  6 */
  7
  8/**
  9 * Adds a wp-block-heading class to the heading block content.
 10 *
 11 * For example, the following block content:
 12 *  <h2 class="align-left">Hello World</h2>
 13 *
 14 * Would be transformed to:
 15 *  <h2 class="align-left wp-block-heading">Hello World</h2>
 16 *
 17 * @since 6.2.0
 18 *
 19 * @param array  $attributes Attributes of the block being rendered.
 20 * @param string $content Content of the block being rendered.
 21 *
 22 * @return string The content of the block being rendered.
 23 */
 24function block_core_heading_render( $attributes, $content ) {
 25	if ( ! $content ) {
 26		return $content;
 27	}
 28
 29	$p = new WP_HTML_Tag_Processor( $content );
 30
 31	$header_tags = array( 'H1', 'H2', 'H3', 'H4', 'H5', 'H6' );
 32	while ( $p->next_tag() ) {
 33		if ( in_array( $p->get_tag(), $header_tags, true ) ) {
 34			$p->add_class( 'wp-block-heading' );
 35			break;
 36		}
 37	}
 38
 39	return $p->get_updated_html();
 40}
 41
 42/**
 43 * Registers the `core/heading` block on server.
 44 *
 45 * @since 6.2.0
 46 */
 47function register_block_core_heading() {
 48	register_block_type_from_metadata(
 49		__DIR__ . '/heading',
 50		array(
 51			'render_callback' => 'block_core_heading_render',
 52		)
 53	);
 54}
 55
 56add_action( 'init', 'register_block_core_heading' );
 57