Available computer php


I would like to know if Asterisk is able to give me the list of computer which are not in communication.
I m explains, I have to make a function of calling-back in php, allowing a customer to be remembered thanks to a simple link on our website.
I need to know how to interrogate asterisk so that it gives me the list of computer available.


(Sorry for my poor english ^^ french student inside :smiley: )