CI doesn't return the view buffer

My problem is when I load a view file, it sends it directly to the browser instead of returning it:

$output=$this->load->view('topic', $data, TRUE); 

I’ve two controllers. Each controller extend another controller before it extend the CI_Controller such as :

topics_admin extends Backend(which extends CI_controller) 

topics extends Frontend (which extends CI_controller)

The first controller behaves as expected but the second one has the problem i’ve explained. There are no major differences between the 2 Frontend & Backend controllers.

I’m using CI开发者_Python百科 2 and I haven’t touched the core classes.

What's wrong with it?

I've found it . There was undefined function in the view and it didn't show the error message because the function was in a tag attribute like that :

<a href="<?=member_url()?>/topics">Title</a>