Resolve IP to Hostname using PHP

Question

How can I resolve an IP address to a hostname using PHP?

Answer 1

Use gethostbyaddr()

$hostname = gethostbyaddr($_SERVER['REMOTE_ADDR']);

echo $hostname;

You might find that this function can hang for some time when an address is not found - if this becomes a performance issue for you, check this manual comment which details a hand-coded method which supports a timeout.