error handling

hi,

im working with php 4 and postgresql 8 and i would like to know how to
handle certain errors generated. in postgresql,  i've written a stored
function that selects a record from a table and in case no record is found i
'raise an exception'. fine, now in my php script  i call that the stored
function which works properly when there is a record but when the record
doesnt exist, i would like to be able to place my own error message and not
e.g  'fatal error, .....'. how do i capture(in php)  the exception i raised
in postgres so that i know the record doesnt exist?


thanx.