wp_render_custom_css_class_name( string $block_content, array $block ): string

122function wp_render_custom_css_class_name( $block_content, $block ) {123	$class_name_attr   = $block['attrs']['className'] ?? null;124	$class_name_prefix = 'wp-custom-css-';125	if ( ! is_string( $class_name_attr ) || ! str_contains( $class_name_attr, $class_name_prefix ) ) {126		return $block_content;127	}128 129	// Parse out the 'wp-custom-css-*' class name added by wp_render_custom_css_support_styles().130	$matched_class_name = null;131	$token_delimiter    = " \t\f\r\n";132	$class_token        = strtok( $class_name_attr, $token_delimiter );133	while ( false !== $class_token ) {134		if ( str_starts_with( $class_token, $class_name_prefix ) ) {135			$matched_class_name = $class_token;136			break;137		}138		$class_token = strtok( $token_delimiter );139	}140	if ( null === $matched_class_name ) {141		return $block_content;142	}143 144	$tags = new WP_HTML_Tag_Processor( $block_content );145	if ( $tags->next_tag() ) {146		$tags->add_class( 'has-custom-css' );147		$tags->add_class( $matched_class_name );148	}149 150	return $tags->get_updated_html();151}