session set code

            if($this->input->post('ajax')) {

                $uploaded_image_ids = $this->Site_model->save_from_url();
                $uploaded_image_id = $this->Site_model->get_last();

                $values = array(
                'image_id' => $uploaded_image_id,
                'session_id' => $this->session->set_userdata('session_id')
                );
                $this->session->set_userdata('edit', $values);

                echo $uploaded_image_ids[0];

            }