"outer" trans_start not rolling back "inner" trans_start records

I know that you can do many queries within one trans_start() call, of course. The problem is that I have a function that can be called by other functions that MAY or MAY NOT call trans_start() first, and there is no way to check this in CodeIgniter.

I've wound up counting with a common model that has wrappers for the transaction functions in codeIgniter:

PHP Code:

function transBegin(){
     $this->_transBegin += 1;
     if($this->_transBegin ==1) {
         $this->db->trans_begin();
     }
}

function transCommit(){
     if($this->_transBegin == 1) {
          $this->db->trans_commit();
     }
     $this->_transBegin -= 1;
}

function transRollback(){
     if($this->_transBegin == 1) {
          $this->db->trans_rollback();
     }
     $this->_transBegin -= 1;
}