problems connecting to php via pg_connect and PGCLUSTER

I have two versions of postgres installed, 8.4 and 9.1 installed on the
same machine

To connect to my 9.1 database, I defined the envromental variable

PGCLUSTER=9.1/main

and use psql to connect via php pg_connect
I have try saying

define("PG_OPTIONS" , "--cluster=9.1/main");

and using the phrase

$con = pg_connect("dbname=".PG_DB." host=".PG_HOST." user=".PG_USER."
options=".PG_OPTIONS);

When I attempt to connect to postgres, I get the error

[Mon Feb 06 22:37:40 2012] [error] [client 127.0.0.1] PHP Warning:
pg_connect(): Unable to connect to PostgreSQL server: FATAL: unrecognised
configuration parameter "cluster" in /var/www/re/php/pgrouting.php on line
33, referer: http://127.0.0.1/re/routing-final.html

Any suggestions as to the correct way of connecting to postgres?

Dave.

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