Select from another database ´....best Way!

Hello,

As far as i know, PostgreSQL doesn't support this feature, so i must do it
by another way.

I need to make a query that will verify if a given element exists in a
table from another database, to implement a foreign key like validation.
The query will be run througth an external script ( PHP ).

A graphical view of the problem:
---------------------------------

( database 1 ) ( database 2 )
--------------- ----------------
| | | |
| TABLE A |<------>| TABLE B |
| | | |
--------------- ----------------

I'd like to hear your opinion on the following solutions:

- Have all the tables( from the 2 databases ) in a unique database, and
use a foreign key constraint.

- Have 2 independent databases. When an insert has to be done, i will
verify if the element exists( other database ). If so i will continue
and commit the transaction. If not i will report the error and
roolback the transaction.

Does PostgreSQL will support this feature soon?

Miguel Carvalho