My PHP interface now works, and there was only one change i needed to
make to my script.
pg_Connect("host=gecko user=... dbname..);
^^^^^
earlier i was putting down localhost here. that kept
getting rejected with auth failures. now that i put down
the host name, it's happy. i woulda thought this wasn't necessary and
perhaps there is still somehting wrong with my pg_hba.conf, but now at
least crypt and password authentication work.
hope this helps anyone else having the same problems.