incoming traffic domain detect - use gethostbyaddr($_SERVER['REMOTE_ADDR'])?

[blackhorse]

if I have a page only allow incoming traffic from certain domain, how should I do that?

use gethostbyaddr($_SERVER['REMOTE_ADDR'])?

What else should I know if I use gethostbyaddr($_SERVER['REMOTE_ADDR']) to detect the incoming traffic is from the domain allowed or not?

Thanks!

[bradgrafelman]

You're going to be making DNS queries each time.

Might be faster to define a range of IP's that are allowed and write up a simple function to see if the IP is within the allowed range. Not sure, though, as it would depend on your DNS setup.

[blackhorse]

the domain check is for a 3rd party site, for a page on my web site, i only allow the incoming traffic from this 3rd party site, and it might change the ip address of its machine, but the domain will be the same. That 3rd party site claims that we shoud check the domain not the ip to tell if it is the incoming traffic from them, due to they might change their ip.