Sometimes when using $_SERVER['HTTP_X_FORWARDED_FOR'] OR $_SERVER['REMOTE_ADDR'] more than 1 IP address is returned, for example '155.240.132.261, 196.250.25.120'. When this string is passed as an argument for gethostbyaddr() PHP gives the following error: Warning: Address is not a valid IPv4 or IPv6 address in...
To work around this I use the following code to extract the first IP address from the string and discard the rest. (If you wish to use the other IPs they will be in the other elements of the $ips array).
if (strstr($remoteIP, ', ')) {
$ips = explode(', ', $remoteIP);
$remoteIP = $ips[0];
}
Hope this helps someone :)
