[...]
while($res = $stmt->fetchColumn(0)) {
[...]

Please pay attention that if the value of the first element retreaved is NULL (in our example here, if the first cathegory doesn’t have a type), you won’t see the others types at all!
To avoid that, you should add a criteria on Type is not null.

I think the setDistinct method still exists in propel 1.3, but the way you retrieve raw results is different. Something like this might work (untested):

 
public static function getTypes() {
  $c = new Criteria();
  $c->addSelectColumn(CategoryPeer::TYPE);
  $c->setDistinct();
  $c->addAscendingOrderByColumn(self::TYPE);
  $stmt = CategoryPeer::doSelectStmt($c);
 
  $types = array();
  while($res = $stmt->fetchColumn(1)) {
    $types[] = $res;
  }
 
  return array_combine($types, $types);
}

This propel upgrade page has a lot of good types to help translate old examples. http://propel.phpdb.org/trac/wiki/Users/Documentation/1.3/Upgrading

Thanks again.