如何在uuid codeigniter中检索最后一个插入ID

i have a trouble when retrieve last insert id in codeigniter. when i try to debug like var_dump(); the output just send int(0)

i use uuid as id with primary key. this is the code:

$this->db->set('id_customer','uuid_short()',FALSE);
    $query = $this->db->insert('customer',$data);
    $id = $this->db->insert_id();
    echo var_dump($id);

    if($query)
    {
        $array = array(
            'kode_trans' => 'uuid()',
            'trans_date' => 'NOW()'
            );

        $this->db->set('id_customer','$id');
        $this->db->set($array,'',FALSE);
        $this->db->insert('transaction_header');

        return $id;
    }else{
        return FALSE;
    }

im newbie in ci. there is something wrong with my code?

The "insert_id" function uses PHP's mysql_insert_id function, which returns "The ID generated for an AUTO_INCREMENT column by the previous query on success, 0 if the previous query does not generate an AUTO_INCREMENT value"

You could try it this way;

$id = uuid_short();
$data['id_customer'] = $id;

$query = $this->db->insert('customer', $data);
if ( $query )
{
    $array = array(
    'kode_trans' => 'uuid()',
    'trans_date' => 'NOW()'
);

$query = $this->db->insert('transaction_header', $array);
return $id; 
}
else
{
    return false;
}