Every form submission gets a unique entry ID which you could use for the order number.
Sounds like you would need to generate a QR code of the URL to the entry (which will contain all the data they submitted) Then, that QR code needs to be embedded in the notification, which they could then print and bring to the photo day. You'd scan that, and your browser would be taken directly o the admin section where their entry is located.
If they have and chose to scan the QR code on their form, out of curiousity, they would just be directed to log in to your site which is not a big deal, since they could not, and everyone is already aware that you can log in to a WordPress site at http://www.example.com/wp-login.php
You would need something to happen before the notification is sent, so you can send the QR code in their notification. The place to do that would be the form_pre_submission_filter: http://www.gravityhelp.com/documentation/page/Gform_pre_submission_filter However, the entry ID is not available at the time of pre-submission: it's generated when the entry is stored. You could use a web service with an API to generate the QR code ( here's one http://qrickit.com/qrickit_apps/qrickit_api.php ) or install a PHP library on your server to generate the QR code ( like http://phpqrcode.sourceforge.net/ ), but in either case, to have the entry ID, it has to happen after the entry is created so you have the ID. By the time you have the ID, the notification was already sent. It's a catch 22.
You could create a QR code at the time of pre-submission, using the gform _pre_submission_filter, but it would have to be comprised of the information they entered into the form, rather than the entry ID. Maybe that is sufficient? At that point though, if they have their printed notification in hand with all the information, your QR code has all the same information and provides nothing new.
Posted 7 years ago on Wednesday February 13, 2013 | Permalink