Postgres + PHP question: username in pg_connect?

I'm getting ready to switch over from MySQL to Postgres for my PHP
application.  Looking over the docs of PHP, it shows a pg_connect
command, which doesn't accept a user name.  Any ideas on how to get it
to connect with a specified user name?  Or do I have to run apache as
a specific user, and have that user have a postgres user account?
Right now, apache is running as nobody, which is pretty normal for
apache.

Thanks,

e