Author: A.Stanislav (30 Sep 07 11:41am)
PHP most certainly will know that have you queried http:BL for each and every IP address you query. But that does not mean they will know those are the visitors to your web site because they do not know why you have looked up an IP address.
And they will not know where the query originated from, the way DNS lookup works. You query your DNS server, which in turn queries the root DNS server for .org, which then queries the DNS server for httbl.org. By the time your query reaches PHP servers, they do not know where the query came from. They do know which specific IP you were looking up with your key. But they do not know it started at your web site.
Also, your DNS server will then cache the result of that query for some time, an hour or so. Any additional queries during that hour (or so) will not hit PHP servers. So, even if a visitor to your web site goes to several web pages (or if you are querying for each image and things like that), PHP will only know that you made one single query about that IP address. But they will not know whether it was your web server doing the querying, or maybe you just manually checking up some random IP address from your home.
So, all they know is what IP addresses you have looked up. But they do not know why you looked them up.
Not much of a privacy concern then (as J.Yard2 pointed out, them looking up your IP reveals their intention to visit your web site to their own ISP, which is potentially more threatening). There is one security concern I can think of, though: Any one of those intermediate DNS servers between your web site (or home) and PHP can use their logs to steal your private key.