PHP & Codeigniter - how to pass parameters to a model?

I am using the following code to initialize a model from within my controller:

$this->load->model('model_name');

Is it possible to modify the above line somehow so that the model constructor recieves a parameter? I want to use the following code in the model constructor:

function __construct($param_var) {
   parent::Model();

   $this->$param_var = $param_var; //I'm not even sure this works in PHP..but different issue
}

This would be very helpful so that I can reuse my model classes. Thanks.

UPDATE: (from one of the answers, my original question is solved..thanks!) Just to explain why I wanted to do this: the idea is to be able to reuse a model class. So basically to give a simple example I would like to be able to pass an "order_by" variable to the model class so that I can reuse the logic in the model class (and dynamically change the order-by value in the sql) without having to create a separate class or a separate function.

Is this poor design? If so could you please explain why you wouldn't do something like this and how you would do it instead?

Solution

I see your reasoning for this, but may I suggest looking at Object-Relational Mapping for your database needs. There is a user-made ORM library for CodeIgniter called DataMapper that I've been using lately. You can use tables in your controllers as objects, and it may be a better fit for your problem.