How to connect using pg_connect function from php3 ?

Hello list!!!
I´ve installed the postgresql 6.5.2-2cl.i386.rpm, the postgresql-devel, the
postgresql-client and postgresql-lib. After, I created the user postmaster
and the user nobody.
I did a php3 script using the next line:
$conn = pg_connect("localhost", "5432", "", "", "ss"),
but didn´t get to do it work and I had the next warning:
Warning: Unable to connect to PostgresSQL server: connectDB() -- connect()
failed:
Is the postmaster running (with -i) at 'localhost' and accepting connections
on TCP/IP port '5432'? in
/home/httpd/html/postgresql/multi.php3 on line 14

Does anybody know how can I do it?
Do I need to change any name of the last parameters that I am using? Do I
need to add others?

If somebody could help me...thanks!!!

Luiz Antonio