Although this works very well for general DNS queries if you want to do a direct DNS query to a specified DNS server (rather than using OS resolution) try PHPDNS: http://www.purplepixie.org/phpdns/
You can do direct (TCP or UDP) low-level queries to a nameserver and recurse at will. Very useful for testing specific servers and also for walking through a recursive resolution.