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

This is slightly off topic, but you can use the PEAR package (or PECL package, I forget which) xdiff to send back good user guidance when you do get a collision.