查看以下几行，了解如何添加自动保存功能：

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\' );