gethostbyaddr() and PHP 4

[Anon]

I would like to list all domain names that resolve to a specific IP address. I read on php.net that gethostbyaddr() might not work on PHP 4 (PHP 4.12). Can anyone confirm this and preferably provide an alternative?

[bretticus]

Just reiterating what someone said in the manual...

"Be cautious when looking up many hostnames. If your DNS server is slow to
respond, you may have to pump up your Max execution time for your scripts,
otherwise, it will timeout. I found that even 3 unresolvable hosts can
cause a 30 second delay in processing.
"

If you're going to run multiple ips through that function, even if it does work, that may not be the best direction to go.

[Anon]

Using gethostbyaddr will only return the hostname that is mapped as the reverse of an IP. That is assuming that the admin of the name server that is authoritative for reverse lookups on that particular IP address maintains their reverses. Gethostbyaddr does not return a list of all domainnames that resolve to a particular IP. You would have to resolve every single resolvable domainname in existence to generate such a list! Not an easy feat, although it could be done.

[Anon]

Thanks...I guess that's a little much to ask of a lil' PHP function.