audit sql queries

Hello,

I am working on auditing interactions with a pgsql database using
php.  So my question is how can i go about obtaining the following
information by only being provided a pgsql query.  I have asked this
same question in a php group however i would also like to ask it here
encase there is a way to do this entirely through postgres.

1. table(s) affected
2. column(s) affected
3. action performed on data (ie. update, insert, select, delete)
4. previous data for each row and column effected (if data changed or
deleted)
5. new data for each row and column effected (or existing data if data
is being selected)

Any help with this would be greatly appreciated.

Thanks,
Dan