- inet_pton: documentation ( source)
<?php
$start = inet_pton('2605:eb00:1000:0123:0100:0100:0000:0000');
$end = inet_pton('2605:eb00:1000:0123:0100:0100:0000:0002');
$myIp = inet_pton('2605:eb00:1000:0123:0100:0100:0000:0001');
echo ($start <= $myIp && $end <= $myIp)?('true'):('false');