This is a simple example of this function, which returns the name of which PostreSQL Database you are currently connected to.
<?php
    $pgsql_conn = pg_connect("dbname=mark host=localhost");
    if ($pgsql_conn) {
        print "Successfully connected to: " . pg_host($pgsql_conn) . "<br/>\n";
    } else {
        print pg_last_error($pgsql_conn);
        exit;
    }
?>
This function is extremely useful for sites which connect to multiple Postgresql services.
Regards,  --mark