Prevent duplicate record insert on manual page refresh

Question

Hi,

I have a problem which has only just surfaced itself.

I'm working in a MVC environment. The method names in my interface class match those of the request module and action i.e. ?module=test&action=action would result in a method called public function test_action() { }

In this particular problem, I have a form which submits to itself. If validation passes, a record is created and I then show the template of another module. This module expects a series of post variables as it is used in two modules.

The problem I'm having is that, if the user successfully passes the validation and attempts to F5 the page, another new record is created etc.

How can I prevent this from happening?

Normally I would header redirect after a successful insert but in this instance I can't.

Answer 1

You can / should re-direct to a new page after successful insertion.

As you are working in MVC, you can add a new controller that just calls the view you want to show.

Answer 2

Developer error:

You need to create a handler page which:

• validating sent data
• insert row
• redirect user

Answer 3

"Normally I would header redirect after a successful insert but in this instance I can't."

are you facing some error in doing that?

Answer 4

If for whatever reason you can't redirect (Which sounds peculiar) you can use the 'same' mechanism used for data validation to flush the forms after a successful insert.

But that's a really ugly way to go.

Answer 5

I would take it a complete other way. I even find redirection an incorrect way of handling this, since changing locations is not meant to overcome logic/form troubles.

The correct solution is:

• Add a unique hash to your form in a hidden input
• Store the hash in a server-side session
• When the form is send, validate the hidden input hash with the hash on your server
• Only execute row insertion when the form validates correctly.

If you are working with Zend Framework, there is a Zend_Form_Element_Hash class for you.