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

Question

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?

Answer 1

You can't pass parameters through the load function. You'll have to do something like:

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

In the model:

function my_constructor($param_var) {
...
}

Response to update:

You could just pass the order_by value when you're calling your model function. I'm assuming in your controller action, you have something like $this->model_name->get($my_id); Just add your order_by parameter to this function. IMO this makes your model logic more flexible/reusable because the way you were doing it, I assume setting order_by in the constructor will set the order_by value for every function.

Answer 2

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.