php - Update Database Field Error CodeIgniter -

i getting following error message in codeigniter 2.1:

a php error encountered  severity: notice  message: array string conversion  filename: database/db_active_rec.php  line number: 1407 

i'm trying update fields in database. have code , every tutorial same batch upload. works anyway thing display such error.

this have in model:

function update2($data){    $this->db->update_batch('users',$data, "id"); } 

this have in controller:

public function updatevalues(){     $this->load->model('get_db');     $newrow = array(         array(             'id' => '3',             'firstname' => 'rapphie'         ),         array(             'id' => '2',             'firstname' => 'charmie'         )     );     $this->get_db->update2($newrow);     echo "it has been updated"; } 

try hope work

function update2($data){    foreach($data $string_val){    $this->db->update_batch('users',$string_val, "id");     } } 

or

function update2($data){    foreach($data $string_val){    $this->db->update_batch('users',$string_val->first_name, "id");     } }