PHP Network Helpers

network_helpers.php

<?php

function is_in_subnet($subnet, $ip)
{
    list($subnet_ip, $subnet_mask) = explode('/', $subnet);
    $begin = (ip2long($subnet_ip) & ip2long($subnet_mask)) + 1;
    $end = (ip2long($subnet_ip) | (~ip2long($subnet_mask))) + 1;
    $ip = ip2long($ip);
    return ($ip >= $begin && $ip <= $end);
}

function cidr2mask($cidr)
{
    return long2ip(-1 << (32 - (int) $cidr));
}

function mask2cidr($mask)
{
    $long = ip2long($mask);
    $base = ip2long('255.255.255.255');
    return 32 - log(($long ^ $base) + 1, 2);
}

function check_subnet($subnet)
{
    if (strpos($subnet, '/') === false) {
        throw new \InvalidArgumentException('IP/CIDR format required for the subnetwork');
    }
    list($ip, $cidr) = explode('/', $subnet);
    $network = (-1 << (32 - (int) $cidr)) & ip2long($ip);
    return $ip === $network;
}