类的PHP调用方法，其中类名在其他类的字段中

I have a CodeIgniter php setup and enhanced it with RESTful capabilities.

I have the following structure

base.php (this is the base controller class

class Base {
    private $model
    public function __construct($model = false) {
        $this->model = $model . '_model';
        $this->load->model($this->model);
    ...
}

And then a controller which specifies a model

class Products extends Base {

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

The problem is as follows: in base.php I have functions for HTTP methods (get, post, put, delete), but I am not able to call a static method from the model like so:

public function get() {
    return $this->model::loadData();
}

If I assign $this->model to a local variable in get() it works, but it looks ugly to me.

So my question is: how can I call a static method of a class A given the class name in a member of class B without assigning it to a new local variable in methods of class B?

P.S.: I know CodeIgniter does not look like this, but the structure of it is irrelevant to my problem.