Multi user application

[eluser]WanWizard[/eluser]
Correct. The sequence is this:

User requests an update form:
- SELECT * FROM table WHERE id = 'something'
- field table.last_update_timestamp contains the timestamp of the last update
- form is displayed, contains a hidden field containing the timestamp value
( you can store it in the session if you don't want to expose it in the form )

User posts the form:
- validate the form
- UPDATE table SET fields, last_update_timestamp = 'new_timestamp' WHERE id = 'something' AND last_update_timestamp = 'retrieved_timestamp_value'.

If this UPDATE returns affected_rows() == 0, than no record was updated, and the assumption is made that this is because of a mismatch of the timestamp. This can be caught so action can be taken.