/**
  *
  *
  * @param Config  $config
  * @param Config  $old_config
  */
 function possible_state_change($config, $old_config)
 {
     if ($old_config->get_string('plugin.license_key') != '' && $config->get_string('plugin.license_key') == '') {
         $result = Licensing_Core::deactivate_license($old_config->get_string('plugin.license_key'));
         if ($result) {
             $this->site_inactivated = true;
         }
         delete_transient('w3tc_license_status');
     } elseif ($old_config->get_string('plugin.license_key') == '' && $config->get_string('plugin.license_key') != '') {
         $result = Licensing_Core::activate_license($config->get_string('plugin.license_key'), W3TC_VERSION);
         if ($result) {
             $this->site_activated = true;
             $config->set('common.track_usage', true);
         }
         delete_transient('w3tc_license_status');
     } elseif ($old_config->get_string('plugin.license_key') != $config->get_string('plugin.license_key')) {
         $result = Licensing_Core::activate_license($config->get_string('plugin.license_key'), W3TC_VERSION);
         if ($result) {
             $this->site_activated = true;
         }
         delete_transient('w3tc_license_status');
     }
 }