Hello Henryi,
I liked a lot your class.
One pointer that I wanted to correct is this:
mssql_insert_id
mssql_insert_id is not a php function. I will make a wrapper for it and send it your way.
Depending on the php version and environment it's possible to use @@INSERTID / on an intranet with very low traffic maybe a MAX(id) can be done as well.
I made an interbase class:
phpclasses.org/browse/package/2353.
...
It will be nice to recode it and addapt it to be another DB available in your class :)
Best regards,
MARTIN