Best way to handle concurrency issues

Question

i have a LAPP (linux, apache, postgresql and php) environment, but the question is pretty the same both on Postgres or Mysql.

I have an cms app i developed, that handle

Answer 1

I suggest: when you first query the record that might be changed, hang onto a local copy. When "updating", compare the copy in the locked table/row against your copy, and if it's changed, kick it back to the user.