When I Use Query Builder Function in codeIgniter, then Error message not shown.
Here Is a Controller
<?php
class Controller extends CI_Controller
{
    public function demo()
    {
        $this->load->model("Model");
        $data["name"] = $this->input->post("text");
        $res = $this->Model->add_data($data);
        echo $res;
    }
}
?>
Here Is a Model
<?php
class Model extends CI_Model
{
    public function add_data($data)
    {
        if ( ! $this->db->insert("table_name",$data))
        {
            $error = $this->db->error();
            return $error["message"];
        }
    }
}
?>