How to make POST method in the same page

I need to send POST method and everything done in the same page. Basically I need to download file, when I download file I want to add +1 to copies_sold field.

This is the query with form:

      <form method="POST" action="/download?key=<?=$strKey;?>">
  <input type="hidden" name="_token" value="{{ csrf_token() }}">
  <input type="submit" name="Submit1" onclick="location='/'">
  </form>

    <?php

    if ( isset( $_POST['Submit1'] ) ){
      $sth = $resDB->exec("UPDATE themes SET copies_sold = copies_sold + 1 WHERE id = '{$id}' LIMIT 1");
    }

     ?>

Do I need here to use some ajax or something ?