Extract Host Name from "gethostbyaddr" string - php

Question

I wish to extract the exact hostname from an ip address but what i am receiving is an entire string of the address.
I would just like to extract only the Host Name from the the string. Can any one point me in the right direction ?
Here is the snippet of the code being used:-
<?php
$ip = $_SERVER['REMOTE_ADDR'];
$fullhost = gethostbyname(gethostbyaddr($ip));
$host = preg_replace("/^[^.]+./", "*.", $fullhost);
?>
Host: <?=$host?>
The output received from it is :-
Host: *.36.64.182.airtelbroadband.in
I would just like to display Airtel Broadband and nothing else to the user

Answer 1

You can try this:
$host = gethostbyaddr($_SERVER['REMOTE_ADDR']); // gets the full hostname
$hostNames = explode(".", $host); // explodes into parts divided by DOT
echo $hostNames[count($hostNames)-2]; // take what you need
// $hostNames[count($hostNames)-1]; -> in
// $hostNames[count($hostNames)-2]; -> airtelbroadband
You might also want to look into geoip.
This is a basic PHP extension that can be installed using PECL.
string geoip_isp_by_name ( string $hostname )
The geoip_isp_by_name() function will return the name of the Internet Service Provider (ISP) that an IP is assigned to.
This function is currently only available to users who have bought a commercial GeoIP ISP Edition. A warning will be issued if the proper database cannot be located.

Answer 2

Consider this simple example:
<?php
$subject = 'Host: *.36.64.182.airtelbroadband.in';
$pattern = '/^Host:\s+((\*|\d+)\.){4}(.+)\..+$/';
preg_match($pattern, $subject, $tokens);
var_dump($tokens[3]);
The output obviously is:
string(15) "airtelbroadband"
That is all the information you can rip from your input. If you really want to somehow show the "publicly known company names" (as opposed to the technical network names), then you need to use some form of catalog. It is very hard to somehow retrieve such information directly from the network. You could give the whois database a try. But parsing the output of that will be a really tough task...