Network Functions

A simple and very fast function to check against CIDR.Your previous examples are too complicated and involves a lot of functions call.Here it is (only with arithmetic operators and call only to ip2long () and split() ):<?php  function ipCIDRCheck ($IP, $CIDR) {    list ($net, $mask) = split ("/", $CIDR);        $ip_net = ip2long ($net);    $ip_mask = ~((1 << (32 - $mask)) - 1);    $ip_ip = ip2long ($IP);    $ip_ip_net = $ip_ip & $ip_mask;    return ($ip_ip_net == $ip_net);  }?>call example: <?php echo ipCheck ("192.168.1.23", "192.168.1.0/24"); ?>

An improved version of claudiu at cnixs dot com not using split and working with the following: ip: 192.168.101.123, CIRD: 192.168.101.144/24 <?php function ipCIDRCheck ($IP, $CIDR) {    list ($net, $mask) = explode ('/', $CIDR);        $ip_net = ip2long ($net);    $ip_mask = ~((1 << (32 - $mask)) - 1);    $ip_ip = ip2long ($IP);    return (($ip_ip & $ip_mask) == ($ip_net & $ip_mask));  }?>

improved version of philippe-at-cyberabuse.org's answer:<?phpfunction cidrconv($net) {     $start = strtok($net,"/");     $n = 3 - substr_count($net, ".");     if ($n > 0)    {        for ($i = $n;$i > 0; $i--)            $start .= ".0";    }     $bits1 = str_pad(decbin(ip2long($start)), 32, "0", STR_PAD_LEFT);    $net = (1 << (32 - substr(strstr($net, "/"), 1))) - 1;     $bits2 = str_pad(decbin($net), 32, "0", STR_PAD_LEFT);     $final = "";    for ($i = 0; $i < 32; $i++)    {         if ($bits1[$i] == $bits2[$i]) $final .= $bits1[$i];         if ($bits1[$i] == 1 and $bits2[$i] == 0) $final .= $bits1[$i];         if ($bits1[$i] == 0 and $bits2[$i] == 1) $final .= $bits2[$i];     }     return array($start, long2ip(bindec($final))); }?>

Here a IP-Range to CIDRs function that I wrote for the purpose of filling my Postfix client.cidr with ripe-ncc data to block spamming from useless countries. Strcmp functions are meant to work around the silly PHP string comparison which inevitably tries compare strings as numbers when possible. I'll make no comment about that fact ... bit I have to bite my tong hard :function PlageVersCIDRs($ip_min, $ip_max) {    $cidrs = array();    $ip_min_bin = sprintf('%032b', $ip_min);    $ip_max_bin = sprintf('%032b', $ip_max);    $ip_cour_bin = $ip_min_bin;    while (strcmp($ip_cour_bin, $ip_max_bin) <= 0) {        $lng_reseau = 32;        $ip_reseau_bin = $ip_cour_bin;        while (($ip_cour_bin[$lng_reseau - 1] == '0') && (strcmp(substr_replace($ip_reseau_bin, '1', $lng_reseau - 1, 1), $ip_max_bin) <= 0)) {            $ip_reseau_bin[$lng_reseau - 1] = '1';            $lng_reseau--;        }        $cidrs[] = long2ip(bindec($ip_cour_bin)).'/'.$lng_reseau;        $ip_cour_bin = sprintf('%032b', bindec($ip_reseau_bin) + 1);    }    return $cidrs;}

PHP miss CIDR functions.

This one will convert a CIDR like this:
0.0.0.0/16 -> 0.0.0.0 - 0.0.255.255
127.0/16 -> 127.0.0.0 - 127.0.255.255
etc...

function cidrconv($net) {
$start=strtok($net,"/");
$n=3-substr_count($net, ".");
if ($n>0) { for ($i=$n;$i>0;$i--) $start.=".0"; }
$bits1=str_pad(decbin(ip2long($start)),32,"0","STR_PAD_LEFT");
$net=pow(2,(32-substr(strstr($net,"/"),1)))-1;
$bits2=str_pad(decbin($net),32,"0","STR_PAD_LEFT");
for ($i=0;$i<32;$i++) {
if ($bits1[$i]==$bits2[$i]) $final.=$bits1[$i];
if ($bits1[$i]==1 and $bits2[$i]==0) $final.=$bits1[$i];
if ($bits1[$i]==0 and $bits2[$i]==1) $final.=$bits2[$i];
}
return $start." - ".long2ip(bindec($final));
}