Extend reminders functionality to cover additional entities and include more tokens

function mymodule_civicrm_getReminderTokens($mapping, $op, &$more) {
  $ent = $mapping->entity;
  CRM_Core_Session::setStatus('Mymodule's getReminderTokens hook is called !');
  if ($mapping->entity == 'civicrm_membership') {
    switch ($op) {
      case 'pre' :
        //
        // one way of adding tokens is adding them directly to the tokens array
        // mind: use a prefix !
        //
        $more->tokens = array(
            'membership.boo' => 'Boo !',
            'mydomain.burp' => 'Scuze me !',
        );

        // 
        // it is possible to amend the selection query, for instance to add 
        // a custom field
        // mind: you need to take a look at BAO/ActionSchedule.php to unerstand how to join these !
        //
        $more->extraJoins[] = 'INNER JOIN civicrm_value_testing_custom_4 cmt ON cmt.entity_id = reminder.entity_id';
        $more->extraFields['widgetizement']   = 'cmt.widgetizement_7 as widgetizement';

        break;

      case 'post' :
        //
        // in the post hook, we can access the resulting dao, and once again
        // add tokens based on any of this info
        //
        $dao = $more->dao;
        $joined = strtotime($dao->join_date);
        $more->tokens[ 'membership.mydate' ] = date('d_m_YY',$joined);

        break;
    }
  }
}