$this->db->set(array('id_categorie' => $id,
                     'id_membre' => $this->auth->id,
                     'titre'=> $titre,
                     'priorite' => $priorite))

                 ->insert('forum_topics');

        $this->db->set(array('id_topic' => //HERE I NEED THE IF OF THE PRECEDENT REQUESTd,
                     'id_membre' => $this->auth->id,
                     'contenu'  => $this->parse_bbcode($this->input->post('RedigerContenu'))))

                 ->insert('forum_messages');

                $redirect = 'forum/topic/'.$id.'-'. url_title(str_replace('/', '', $titre_topic->titre));

                    return redirect($redirect);