Syntax in function does not work

You have no class defined, so you cannot use the this keyword. This is the way to build a controller (but the db stuff should come from a model).

PHP Code:

class Example extends CI_Controller {

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

    public function index()
    {
       $test = $this->db->query("SELECT name FROM users"); // you should hava a where clause to fetch on dataset
       echo $test->row()->name;                            // or call the result by a loop
    }
} 


You call this with yoursite.tld/example

Ou...yes, it works. But I need to use more queries and I want them to use in all files.
For example:

I have files called header.php, content.php, footer.php, function.php.
I want to use in all files function(). Without function() it works correctly.

Is it possible set up it globally?