I have a self-rolled MVC framework that I am building, and up to this point have managed to avoid the need for any AJAX calls. Now, however, I\'d like to create a real-time
Best practice would be to disregard the fact it's an AJAX request entirely and to only concern yourself with what controller your AJAX request is pertinent to. If you were to have a catch-all AJAX controller you'd likely be grouping apples to pears, so to speak.
The main difference is that for AJAX requests you will likely need to avoid setting any layout (and more than likely view) data. This can easily be remedied by having a method in your parent Controller class which checks for valid AJAX requests:
protected function isAjax()
{
return (isset($_SERVER['HTTP_X_REQUESTED_WITH']) &&
$_SERVER['HTTP_X_REQUESTED_WITH'] == 'XMLHttpRequest');
}