New chmlib PHP binding

Hi:

My name is Jesús Espino, and i'm programming my first PHP Extension,
that is a binding of the chmlib for easy access to the chm files.

The code can see here https://redmine.jesusespino.org/projects/phpchm/repository

I want to include it on the PECL repository, but first i want to get
suggestion of changes (i have tried to follow the coding style and
recomendations of PHP).

And i have a doubt about Objects constructor. If i can't construct a
object, how i say in C that there are a exception or no return an
object.

Greetings.