Modifying the checkout process - making "comments" a required field - urgent

[AuroraMedia]

I need to make the Comments/Special instructions text area field on the checkout process (page 2 of 3) a compulsory field. The process should not advance to page 3 unless this field has some data.

Could someone please advice on how to implement this.

Thanks in advance.

[AuroraMedia]

We urgently need to make the Comments / Special Instructions field appearing at the end of the Checkout Page 2 of 3 a compulsory field.

The Checkout should not proceed to Step 3 unless this field has some data.

What modifications do I need to do to ensure that?

Please advice.

Thanks all.

[DrByte]

This is the concept which you can work with to build your custom coding:
/includes/modules/pages/checkout_confirmation/header_php.php
around line 44 you have:

if (isset($_POST['payment'])) $_SESSION['payment'] = $_POST['payment'];
$_SESSION['comments'] = zen_db_prepare_input($_POST['comments']);

Add the check to enforce not-empty content:

if (isset($_POST['payment'])) $_SESSION['payment'] = $_POST['payment'];
$_SESSION['comments'] = zen_db_prepare_input($_POST['comments']);
if ($_SESSION['comments'] == '') {
  $messageStack->add('checkout_payment', 'Please enter order comments before proceeding.', 'error');
  zen_redirect(zen_href_link(FILENAME_CHECKOUT_PAYMENT, '', 'SSL'));
}

[AuroraMedia]

Thanks a million DrByte. Your suggestion was all that was needed to get it working. Only the add('checkout_payment'...... had to be changed to add_session('checkout_payment'.... to get the error prompt to show on the frontend.

It is now working just as we had wanted. Thanks again.

AuroraMedia