Creating Ancillary Classes

In some cases you may want to develop classes that exist apart from your controllers but have the ability to utilize all of CodeIgniter’s resources. This is easily possible as you’ll see.

get_instance()

get_instance()

Returns:	Reference to your controller’s instance
Return type:	CI_Controller

Any class that you instantiate within your controller methods can access CodeIgniter’s native resources simply by using the get_instance() function. This function returns the main CodeIgniter object.

Normally, to call any of the available methods, CodeIgniter requires you to use the $this construct:

$this->load->helper('url');
$this->load->library('session');
$this->config->item('base_url');
// etc.

$this, however, only works within your controllers, your models, or your views. If you would like to use CodeIgniter’s classes from within your own custom classes you can do so as follows:

First, assign the CodeIgniter object to a variable:

$CI =& get_instance();

Once you’ve assigned the object to a variable, you’ll use that variable instead of $this:

$CI =& get_instance();

$CI->load->helper('url');
$CI->load->library('session');
$CI->config->item('base_url');
// etc.

If you’ll be using get_instance() inside another class, then it would be better if you assign it to a property. This way, you won’t need to call get_instance() in every single method.

Example:

class Example {

        protected $CI;

        // We'll use a constructor, as you can't directly call a function
        // from a property definition.
        public function __construct()
        {
                // Assign the CodeIgniter super-object
                $this->CI =& get_instance();
        }

        public function foo()
        {
                $this->CI->load->helper('url');
                redirect();
        }

        public function bar()
        {
                $this->CI->config->item('base_url');
        }
}

In the above example, both methods foo() and bar() will work after you instantiate the Example class, without the need to call get_instance() in each of them.