mb.php

function hcf_save( $post_id ) {
	if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
		return;
	}
	if ( $parent_id = wp_is_post_revision( $post_id ) ) {
		$post_id = $parent_id;
	}
	$field_list = [
		'hcf_author',
		'hcf_published_date',
		'hcf_price',
	];
	foreach ( $field_list as $fieldName ) {
		if ( array_key_exists( $fieldName, $_POST ) ) {
			update_post_meta(
				$post_id,
				$fieldName,
				sanitize_text_field( $_POST[ $fieldName ] )
			);
		}
	}
}
add_action( 'save_post', 'hcf_save' );