Auto commit Off how will it effect us ?

Dear all ,

Permit me to gain some of your most valuable knowledge ...........

Our intrAnet server has the following spec
1. RH 9.0
2. Postgresql 7.3.4
3. PHP 4.3.3
4. GCC  3.2.2

Till date my front end language (PHP) use to simply pass the data to
postgresql in case of insert and
update we were not using
1  BEGIN COMMIT block in PHP till date thanks to auto-commit-ON in postgreql
2. ROLLBACK script in PHP script


And now when our company has decided to switch over to  postgresql 7.4
we have some doubt
1. Do we have to include BEGIN and COMMIT block around the insert
process . (Because Postgresql 7.4 has auto-commit-OFF) in our PHP scripts
2. Not only this do we also have to port the pgSQL functions which use
to do inserts into a third table such that
    data gets committed on function execution


Please provide us any kinda information so that we can happily switch to
postgressql 7.4



Regards,
V Kashyap