Обсуждение: postgres error

hi,

i am running php3,apache1.3.9,postgresql6.4 on a redhat 6.0 m/c.
i have written php scripts to connect to a postgres database to
access data on aweb environment.
when i connect to a table i am not supposed to , i get a postgresql
error saying operation not allowed.

1)how can i trap this error,so that i can write codes to return some
of my own error message rather than the back end one ?

2)how can i get   grant /revoke permissions for a user through a php
script(for that matter any cgi script)? 
\z doesn't seem to give anything.

any help regarding this will be highly appreciated.

-anjan