Retain your Social Proof after domain changes via AddThis and PHP

I thought I’d share this as it helped me to keep my social data counts.

Based on a post at this link, I built out a AddThis’s “data-url” to dynamically present the old domain for posts older that the cutover date. Newer posts remain unaffected:

<!--
Let's alter the domain based on post date
-->
  <?php

  $url_change_date = strtotime("11/6/2015");
  $post_date = strtotime(get_the_date());

  $sharing_url = get_permalink();

  if ($post_date < $url_change_date) {
        $url_date_prefix = "/" . date("Y", $post_date) .
                                       "/" . date("m", $post_date);

        $sharing_url = str_replace("://new-domain-name.com",
                                               "://old-domain-name.edu",
                                               $sharing_url);
   }

  // At this point, $sharing_url is the correct URL to present
  //  to the social sharing APIs in order to maintain counters.
   ?>
  <div class="addthis_sharing_toolbox" data-url="<?php echo $sharing_url ?>" data-title="<?php the_title(); ?>"></div>

Note: be sure to include this code in both your single.php and index.php templates. See the original post mentioned above for a lengthy description of the issue.