$db=pg_Connect('localhost', 5432,  "", "", 'twig');
if (! $db) {
  PrintError("Could not connect to database");
  return 0;
}

PHP3 CONFIGURATION:
./configure --with-pgsql=/usr/local/pgsql  \
        --with-apache=/u/dinh/apache_1.3.6 \
        --enable-track-vars --with-imap=/u/dinh/imap-4.5 \
        --with-gd=/u/dinh/gd_1.3 --with-x --with-zlib \
        --with-config-file-path=/usr/local/etc/

I am able to connect to the Postgres database by running
   pgsql twig

When running the above php3 code by opening the URL
http://mandrake.es.hac.com/twig/test.php3, I received the following
error message:
  Warning: Unable to connect to PostgresSQL server: connectDB()
  failed: Is   the postmaster running and accepting TCP/IP(with -i)
  connections at  'localhost' on port '5432'? in features/pgsql.db.inc
  on line 35
  Error: Could not connect to database Failed!