PHP Manual: Get the Autonomous System Numbers (ASN)

string geoip_asnum_by_name(string $hostname)

The geoip_asnum_by_name function will return the Autonomous System Numbers (ASN) associated with an IP address.

Returns the ASN on success, or false if the address cannot be found in the database.

Example #1 A geoip_asnum_by_name example

This will output the ASN of the host www.example.com.

<?php
$asn = geoip_asnum_by_name('www.example.com');

if ($asn) {
    echo 'The ASN is: ' . $asn;
}
?>

The above example will output:

The ASN is: AS15133 EdgeCast Networks, Inc