Magic behind loading model in codeigniter

Question

Guys before few days I went for interview,and interviewer asked me a question,which is still only question and I could not find its answer.

To Load a Model In Codeigniter 
we do,
$this->load->model('xyz_model');
then magically 
$this->xyz_model->function_of_xyz_model();
Above line lets us access function of 'xyz_model' 
named'function_of_xyz_model'

How it all happen,which game is played under the carpet to do all above. As I'm not well experienced in OPP so please point out the concepts(if any) used inside.

Answer 1

I imagine something like this (although it`s very robust and many validations should be done beforehand), magic methods are the key :

class ControllerOrSimilar {
    /**
    * Loader
    */ 
    var $loader;
    public function __get($instance) {
        //retrieve static instances loaded in class Loader
        return Loader::$instances[$instance];
    }
}

class Loader {
    static $instances = array();
    public function load($modelRequested) { //instanciate in static variables to be accessed globally 
        if(!$this->$instances[$modelRequested]) {
            $this->$instances[$modelRequested] = new $modelRequested();
        }
    }
}

Although the actual implementation I think it`s different, I have worked with codeigniter but never gone in the depts of the implementation