rollback in MySQL?

[Anon]

I am trying to build a button which calls a script that "undo" the last transaction. How do you do it in PHP with MySQL?

[ymichel]

Actually there is no way to commit nor rollback. All transactions are "autocommited" cause of the fact that mysql doesn't support transactionhandlit, yet.
as a workaround you may keep your actions inan additional table to manualy rollback these statements.

[[deleted]]

MySQL is capable or transactions, but only if you use the berkeley library (see the website for more info)

Whats more to the point is that you can only rollback on the same database connection that you issued the queries you want to rollback on. But, HTTP is a stateless protocol, you can never be sure which connection a user gets. So you'd have to find a way of making sure that every user get's his own database connection, and that they will continue to use the same connection every time they do something in the database.

And then, what if a user forgets to commit his work, or his browser crashes, or his internet link is broken...
Lot's of challenges there I think.

[jcleary]

Vincent,

Would it be possible to keep the connection open by storing the connection number as a session variable, or does PHP close the connection once the page is loaded?

If it does close the connection, you would probablly have to write a php application that ran in the background and held connections open. Probably would have a timeout after which it would commit data? Like you say, lots of work!

[[deleted]]

You could use pconnect to keep connections open,
but how would you force a particular script to use a particular connection?

All variables and identifiers used by a script are destroyed when the script ends, so storing a connection id is useless.

I suppose you could try to make your own database-server interface, that listens on a socket so you can talk to it. That script could stay running, thus keeping the connections open and identified.
Then you could send all your commands to that script, along with something like a session ID to select the correct connection...

[carfield]

I just wonder if there any function of php support mysql to rollback?