That seems to be unrelated to the concern here (as belied by the grandparent citing magic_quotes). XHP (like plain PHP, for that matter) can be used in a way that, for all intents and purposes, separates the concerns of presentation and logic. It's more a matter of convention than constraint.
The purpose of a "layer" is not determined by the language it's implemented in, but by what the code actually does. Code that handles nothing but presentation is by definition separate from the business logic, even if the presentation code and business logic are implemented in the same language. It is trivial to implement this architecture with PHP and even easier with XHP.
