Mini-plugin to add an additional Google Analytics tracking code to web stories.

web-stories-additional-gtag.php

<?php
/**
 * Plugin Name: Web Stories Custom Google Analytics
 * Description: Mini-plugin to add an additional Google Analytics tracking code to web stories.
 * Plugin URI: https://wp.stories.google/
 * Author: Pascal Birchler, Google
 * Author URI: https://opensource.google.com/
 * Version: 0.0.1
 * License: Apache License 2.0
 * License URI: https://www.apache.org/licenses/LICENSE-2.0
 */

add_action(
    'web_stories_print_analytics',
    static function () {
        // TODO: REPLACE WITH YOUR OWN GOOGLE ANALYTICS MEASUREMENT ID.
        $tracking_id = 'G-12345';

        ?>
      <amp-analytics type="gtag" data-credentials="include">
        <script type="application/json">
          {
            "vars": {
              "gtag_id": "<?php echo esc_attr( $tracking_id ); ?>",
              "config": {
                "<?php echo esc_attr( $tracking_id ); ?>": {
                  "groups": "default"
                }
              }
            },
            "triggers": {
              "trackClickThrough": {
                "on": "story-click-through",
                "tagName": "a",
                "request": "click ",
                "vars": {
                  "event_name": "custom",
                  "event_action": "story_click_through",
                  "event_category": "${title}",
                  "send_to": "<?php echo esc_attr( $tracking_id ); ?>"
                }
              },
              "pageAttachmentEnter": {
                "on": "story-page-attachment-enter",
                "request": "event",
                "vars": {
                  "event_name": "custom",
                  "event_action": "story_page_attachment_enter",
                  "event_category": "${title}",
                  "send_to": "<?php echo esc_attr( $tracking_id ); ?>"
                }
              }
            }
          }
        </script>
      </amp-analytics>
        <?php
    }
);