Message: Cannot modify header information - headers already sent by

parent::Controller();

  function __construct(){
    parent::Controller();
  }

function Login(){
  parent::Controller();
}

<?php
class Login extends Controller{
    function Login(){
	parent::Controller();
	$this->load->library('session'); // untuk load session library
    }
 
    function index(){
	if ($this->session->userdata('login') == TRUE){
	   redirect ('main/member');
		}else
		{
			$data['dynamiccontent'] = 'form_login';
			$this->load->view('templates/template.php', $data);
		}
    }
 
    function validate_login()
    {
        $this->load->model('memberlist');
        $sql = $this->memberlist->validasi();
        if ($sql)
        {
            $session = Array('username' => $this->input->post('username'), 'login' => true);
            $this->session->set_userdata($session);
            redirect('main/member');
        }
        else
        {
            $this->index();
        }
    }
}
?>