Re: Preventing multiple submits

At 02:45 AM 8/25/00 -0300, Manuel Lemos wrote:

[snip] The best solution for really preventing more that one submission of the same form on the server side is to use create a unique key and pass it in the form as hidden field. Store the key in a database (session data area is ideal for this). When the first form submission is received, check if the key exists in the database, delete it, accept the form. On further submissions, check that the key does no longer exist and warn the user that the form was already submitted.

The user's session id will serve very nicely as the unique key. That is why I say that only a counter is needed.

I know that JavaScript (or any other Client-Side tool) has its limitations as noted by you before, but with it you will stop the second submission before it is actually sent. The first script will run normally and return its output to the browser, without knowing that the user tried to send the form for a second time. The browser will no cancel that first connection, because it is not posting a second form. Right, you may want to check this PHP form generation and validation class. It has an option to let you specify a text that is used to pop up a confirmation box with Javascript that asks the user if he really means to submit the form again. The user may confirm or cancel the form submission. This really works great since most of the times you just want to prevent nervous users to submit forms more than once creating inadverted duplicate database entries. http://phpclasses.UpperDesign.com/browse.html/package/1

The class is more mature and feature-rich than any other form generation/validation script that I have run across (or written for that matter :) - however, it might be a bit intimidating for a new user! I suppose that one thing to consider is that javascript is a nice clean way to stop most re-submissions. PHP can be used along with the js to ensure robust behavior. - zak