whois with php

Hi there, I'm trying to make a simple tool that make a simple check for the availability of a domain name in a certain top-level domain. I use gethostbyname and if it fails, it means the domain is probably not registered. It works great for domains.COM, domains.NET, domains.CA and all domains.[province].CA. However it does not work with biz, org, info or name since all unavailable domains (the ones that are not yet registered) are pointing automatically to some registrar. Anyone have an idea on how to go around this without having to reverse engineer the whois databases? (BTW, is it legal to do such reverse engineering?) Thanks, xm