Error"Unable to connect to PostgresSQL server: connectDBStart()" - Mailing list pgsql-php

hello,
        I am using PHP to connect to postgresql server. Till now it was
working fine and PHP was connecting sql server without any problems.
Suddenly today i am getting an error or warning which says
'Warning:
Unable to connect to PostgresSQL server: connectDBStart() -- unknown
hostname: localhost in /var/www/html/phpfiles/others/othersbrowse.php on
line 20
                 Warning: Supplied argument is not a valid PostgreSQL link
resource in /var/www/html/phpfiles/others/othersbrowse.php on line 25
                                                        ERROR IN
EXECUTION'


I am not getting what the problem was. Beform some times it used to come
but when i restarted the system it used to work fine.
Pls anybody tell me what the problem is and any suggestions pls since the
server has to run all the 24 hours and 365 days.
        thanks in advance
              Arun