I've not used PowerDNS, but from a quick scan of their docs it looks like you just need to run a simple MySQL query to create an A record - an A record is what allows a lookup from hostname to IP address.
INSERT INTO records (domain_id, name, content, type,ttl,prio)
The first rule of Tautology Club is the first rule of Tautology Club.
Ah, alright. This whole PowerDNS thing is tough for me to wrap my head around. When the new record is inserted into the database, is there a PowerDNS process that auto-propagates the new record to the interweb, or do you have to shell_exec() and reload httpd or whichever process handles DNS?