Question

I’m currently working on a project where we are developing an application that will be used to power content on multiple sites from a single set of files / hosting environment.

There are a number of PHP classes with names such as model_account and model_vehicle which are defined in seperate files named the save as the class name. We are using spl_autoload_register to load the class files as below (simplified):

function my_autoloader($class_name) {
    if(substr($class_name, 0, 6)=='model_') {
        require_once('models/'.$class_name.'.php');
    }
}

What we want to do, is if the visitor is accessing site xxx and we create an instance of a class, eg $account = new model_account(); – actually create an instance of class model_xxx_account if the file exists (models/model_xxx_account.php), but if it doesn’t, just include the models/model_account.php file and create an instance of model_account.

Likewise, if a visitor came from site yyy, we would want to use model_yyy_account if exists, but full back to model_account if it doesn’t.

Essentially what we wish to do is create an instance of a different class if conditions are met, but from the same instantiation call.

We’re not using an off-the-shelf framework like CI or Cake. Also, I’ve slightly simplified the naming conventions for this post. Sorry if my OO terminology isn’t spot on.

Answer 1

It actually sounds like you should be using some sort of factory pattern to deal with your class loading.

If you do $account = new SomeClass(), it does not make any sense to ever really end up with an object of class Bumblebee.

You should technically have some sort of account factory that decides which class to give you.

You code will end up looking more like $account = AccountFactory::retrieveModel(), which then can determine which model you want to load WITHOUT delegating to your autoloader.

The point of the autoloader is to essentially say “I want THIS exact class”, and isn’t to be wibbly wobbly or in particular be making any sort of decisions of that sort. Your factory can actually go through your file structure and determine which class to pass back in the function call, and in your code you aren’t relying on new to get the model you want, since it seems in theory all of your account models will be sharing the same interface or at least extending model_account.

AccountFactory can essentially say, “model_yyy_account exists, thus return new model().