public function addcart(){
    if(isset($this->session->userdata)){
        $type = $this->session->userdata('type');
        $username = $this->session->userdata('username');
         $this->db->select('id_product ,price');
         $query = $this->db->get('product', array('title'=> $this->input->post('title')));

         if($query->num_rows() >0){
            $row = $query->row();
            $data = array(
            'id'     => $row->id_product,
           'qty'     => $this->input->post('quantity'),
           'price'   => $row->price,
           'name'    => $this->input->post('title'),
           //'options' => array('Size' => 'L', 'Color' => 'Red')
        );

        $this->cart->insert($data);
        }
    }
}

public function addcart(){
    if(isset($this->session->userdata)){
        $type = $this->session->userdata('type');
        $username = $this->session->userdata('username');
         $this->db->select('id_product ,price');
         $query = $this->db->get('product', array('title'=> $this->input->post('title')));

        $cart['product'] = $this->cart->contents(); // get previous data from cart
         if($query->num_rows() >0){
            $row = $query->row();
            $id = $row->id_product;
            $cart['product'][$id] = array(
            'id'     => $row->id_product,
           'qty'     => $this->input->post('quantity'),
           'price'   => $row->price,
           'name'    => $this->input->post('title'),
           //'options' => array('Size' => 'L', 'Color' => 'Red')
        );

        $this->cart->insert($cart); //update cart
        }
    }
}