Actually figured it out using cookies…

Added this to my themes custom js file…

var mySubmitController = Marionette.Object.extend( {  
  initialize: function() {
    this.listenTo( Backbone.Radio.channel( 'forms' ), 'submit:response', this.actionSubmit );
  },

  actionSubmit: function( response ) {
    // delete any old subid cookies... (probably not necessary since we're (re)setting it below but whatever)   
    document.cookie = 'subid=;expires=Thu, 01 Jan 1970 00:00:01 GMT;';
    var subID = response.data.actions.save.sub_id;
    // just to make sure we're getting the correct sub_id...
    console.log('SUB ID: ' + subID); 
    // you can see all the data for this form submission...
    console.log(response);
    // set a cookie to hold the sub_id...
    document.cookie = 'subid=' + subID + '; expires=Thu, 31 Dec 2030 12:00:00 UTC; path=/';
  },
});

jQuery( document ).ready( function( $ ) {
    // Instantiate our custom field's controller, defined above.
    new mySubmitController();
});

At this point you should have a cookie ‘subid’ with a value of the submission id. You can do with that whatever you need. I’m getting/displaying mine on the redirect page with php:

$sub_id = $_COOKIE['subid'];
echo 'sub_id: ' . $sub_id;

There may be a more reliable and efficient way to do this but this works for my purposes.

• This reply was modified 6 years ago by shagdirty.