您需要使用save_post 与一起采取的行动wp_insert_post() 函数。像下面这样的方法可能会奏效。

function tnc_update_car_details( $post_id, $post, $update ) {

    // If this is a revision, don\'t continue
    if ( wp_is_post_revision( $post_id ) )
        return;

    $post_type = get_post_type($post_id);

    // If this is not an invoice post type, don\'t continue
    if($post_type !== \'invoice\')
        return;

    $car_id = \'1\';

    wp_insert_post(
        array(
            \'ID\' => $car_id,
            \'meta_input\' => array(
                \'km_travelled\' => \'300\',
            ),
        ),
    );
}
add_action( \'save_post\', \'tnc_update_car_details\', 10, 3 );