Application Transaction Question... Postgres 8.3.6 - PHP 5 - Solaris 10

Hello,

I am creating an application in PHP that accesses a Postgres
database.  This application works, but I have been unable to perform a
database task that is extremely important.  My application is a admin
app that allows a user to insert records into several tables in a
database.  The basic model is to put a record into two base tables
then join the tables with a bridge table.  Obviously, this needs to
run the queries as one transaction.  I have been unable to find a way
to make this work.  I'm using the pg_query_params function to insert
the records.  I tried using pg_query and issuing the begin and commit
in separate queries, but that doesn't work.  Can someone tell me how
to do this.

Thanks,
Carol