Is it possible to stop a webform form during submission?

Question

The webform module is being used for a form that takes a payment. The data is validated as much as it can and then in a submit handler it is finally sent to the payment processor.

The result can be a failure (wrong card number, or no funds etc.), which should result in the form being re-presented giving the user the opportunity to check their fat fingers didn't type in the wrong card details, try another card etc.

In a vanilla Drupal form I could do a $form_state['redirect'] = FALSE; and it would return the form as-is, but this does not work when working within webform because it deals with that itself.

So this is a weird one because it's basically validation done in a submit handler. This is because we need to make sure everything's valid before submitting it to the third party, but there are clearly two ways to frame this question:

1. As the title says, is it possible for a submit handler to tell webform to stay on this page and not consider it complete?

   or

2. If I move the submission code into a validation handler, how can I ensure my validation handler happens after all the others, and then check that there aren't any other validation errors before I proceed with the payment submission?

Answer 1

First is I'm not sure if it's best practice to do validations in the submit handler because as you've said, you need to validate first. So I can only answer your second question.

To make your validation run after every validation present for that form, you need to add it in the end of the #validate attribute. Example is like:

$form['submit']['#validate'][] = 'your_last_needed_validation_func';

To check if there are validation errors before your validation function, you can use the form_get_errors function.