Adding functionaly to cotroller

[eluser]Unknown[/eluser]
Hello.

I often use the same block of code for outputing status of execution of my functions in json format. for example:

Code:

$this->output->set_content_type('application/json');
  $this->output->set_output(json_encode(array('status' => 'success')));

1. How can I make a function that will be accessible in each controller? I think I should change something in system folder, but I'm just not sure

2. When I write a function in controller, often I have next logic: if I get wrong get/post data, or maybe user is not logged, etc I send status in json format, something like "status":"error", and then die. But $this->ouput->set_output() works for me only if I put it in the end of functon. I know that I should do any output once in the end, but for example:

Code:

public function myfunc() {
     $this->output->set_content_type('application/json');
     if (!$this->input->get('param')) {
           // here I should send an error, and then die.
           $this->output->set_output(json_encode(array('status' => 'error')));
           die;
           // and that's it. I won't send any data further
     } else {
           // here I do something and then send results
           $this->output->set_output(json_encode($result)));
     }
}

Instead I want to use my own function, like $this->setStatus('error', 3) (3 is error number for example), or maybe $this->output->sendStatus('error', 3) and do it not only in the end, because sometimes it makes functions harder to construct

Thanks in advance