Obtain primary key value generated by before-insert trigger

[Ross Goldberg]

Is there any way to obtain a primary key value generated by a before-insert trigger?

I know that last_insert_id() can return the first value of an auto_increment column from a previous insert, but I can't seem to get it to work with a trigger-generated primary key.

There is no other unique key on my table, so I won't be able to perform a subsequent select to determine the generated primary key from data that was used in the insert.