Handling error messages

Hi:

One of the most obvious things that should do a database is to check
for data integrity and values, but programming with PHP and other
languages I see that we duplicate this task: one on the client side
(with javascript), sometimes on server side (on PHP) and finally
on the database server.

I think the server-side check could be made more easily if the database
server could return error messages in a way we can handle them. For
example, giving an error id (also helpful to translate) and the column and
row affected.

Could be this implemented on Postgres?

--
Víctor R. Ruiz
rvr(at)idecnet(dot)com