Anonymize the last two octets of an IP address, by replacing it with 0 (zero)

anonymize-ip.php

<?php
$octets = explode('.', $ip);

/**
 * Instead of using Regex and str_replace, we're slicing the array parts
 * and rebuilding the ip (implode) to make sure no duplicate values are
 * replaced.
 * 
 * E.g. using str_replace or preg_replace; 192.168.1.1 would result in 092.068.0.0.
 */
$second_to_last     = array_slice($octets, -2, 1, true);
$second_to_last_key = array_key_first($second_to_last);

$second_to_last[$second_to_last_key] = '0';

$last     = array_slice($octets, -1, 1, true);
$last_key = array_key_first($last);

$last[$last_key] = '0';

/**
 * Replace each octet with the with the 
 */
$octets = array_replace($octets, $second_to_last, $last);

return implode('.', $octets);