I have some trouble to execute a Python file from a Codeigniter controller's function.

~/application/controllers/Lights.php :

```
header("Access-Control-Allow-Origin: *");
class Lights extends CI_Controller {
    public function __construct() {
        parent::__construct ();
        $this->load->helper ( array ('url', 'form') );
    }
    public function turnOn() {
        system('sudo python test.py > /dev/null 2>/dev/null &');
    }
}

```

but when I try to execute a system call, like :

```
system("sudo gpio mode 15 out");

```

this works perfectly.