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    User Contributed Notes 14 notes

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    36
    claudiu at cnixs dot com
    17 years ago
    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"); ?>
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    11
    Anton Avramov - lukav at lukav dot com
    7 years ago
    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));
      }
    ?>
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    5
    Anonymous
    8 years ago
    improved version of philippe-at-cyberabuse.org's answer:

    <?php
    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);
            $net = (1 << (32 - substr(strstr($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)));
    }
    ?>
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    2
    David GASTALDIN
    17 years ago
    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;
    }
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    2
    philippe-at-cyberabuse.org
    22 years ago
    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));
    }
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    -1
    -dR
    9 years ago
    This little function might come in handy

    <?php
    function cidr_range( $cidr, $chkip=null )
    {
            // Assign IP / mask
            list($ip,$mask) = explode("/",$cidr);

            // Sanitize IP
            $ip1 = preg_replace( '_(\d+\.\d+\.\d+\.\d+).*$_', '$1', "$ip.0.0.0" );

            // Calculate range
            $ip2 = long2ip( ip2long( $ip1 ) - 1 + ( 1 << ( 32 - $mask) ) );

            // are we cidr range cheking?
            if ( $chkip != null && ! filter_var( $chkip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4) === false )
        {
            return     ip2long( $ip1 ) <= ip2long( $chkip ) && ip2long( $ip2 ) >= ip2long( $chkip ) ? true : false;
        } else {
            return     "$ip1 - $ip2";
        }
    }

    var_dump( cidr_range( "127.0/16", "127.0.0.1" ) );   // bool(true)
    var_dump( cidr_range( "127.0/16", "192.168.0.1" ) ); // bool(false)
    var_dump( cidr_range( "192.168.0.0/24" ) );          // string(27) "192.168.0.0 - 192.168.0.255"

    ?>
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    -1
    nexxer at rogers dot com
    19 years ago
    In Trevor Hemsley's translation of the perl range2cidr function, the

    while ($end > $start)

    condition should be

    while ($end >= $start)

    otherwise it won't work for /32s, ie if you feed range2cidr("1.2.3.4", "1.2.3.4").

    -- nex
    up
    -3
    Anonymous
    21 years ago
    Alternative cidr_conv function - a little easier to follow

    function cidr_conv($cidr_address) {
      $first = substr($cidr_address, 0, strpos($cidr_address, "/"));
      $netmask = substr(strstr($cidr_address, "/"), 1);

      $first_bin = str_pad(decbin(ip2long($first)), 32, "0", STR_PAD_LEFT);
      $netmask_bin = str_pad(str_repeat("1", (integer)$netmask), 32, "0", STR_PAD_RIGHT);
     
      for ($i = 0; $i < 32; $i++) {
        if ($netmask_bin[$i] == "1")
          $last_bin .= $first_bin[$i];
        else
          $last_bin .= "1";
      }

      $last = long2ip(bindec($last_bin));

      return "$first - $last";
    }
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    -4
    samuele at norsam dot org
    20 years ago
    To find if an IP is in a net/mask (very fast):
    <?php
    function isIPIn($ip,$net,$mask) {
           $lnet=ip2long($net);
           $lip=ip2long($ip);
           $binnet=str_pad( decbin($lnet),32,"0","STR_PAD_LEFT" );
           $firstpart=substr($binnet,0,$mask);
           $binip=str_pad( decbin($lip),32,"0","STR_PAD_LEFT" );
           $firstip=substr($binip,0,$mask);
       return(    strcmp($firstpart,$firstip)==0);
       }
    ?>

    This function can be compacted, avoiding some variable settings, but the function will not be too clear to read...
    Example code, used to made a kind of location service network-based:

    <?php
    $n     = array ( "192.168.0.0/16"   => "TUSCANY",
                     "192.168.1.0/24"   => "- Florence",
                     "192.168.2.0/24"   => "- Pisa",
                     "192.168.3.0/24"   => "- Siena",
                     "192.168.64.0/21" => "- Tuscan Archipelago",
                     "192.168.64.0/23" => "--- Elba Island",
                     "192.168.66.0/24" => "--- Capraia Island",
                     "192.168.67.0/24" => "--- Giannutri Island");

    // Normally you should use the following line
    $myip = $HTTP_SERVER_VARS['REMOTE_ADDR'];
    // This is first example: returns Tuscany/Pisa
    $myip = "192.168.2.33";
    // This is second example: returns Tuscany/T.Arch./Elba
    $myip = "192.168.65.34";

    echo     "Your position:<br />\n";
    foreach (     $n as $k=>$v ) {
       list(    $net,$mask)=split("/",$k);
       if (    isIPIn($myip,$net,$mask)) {
           echo     $n[$k]."<br />\n"; }
       }
    ?>

    and so on...
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    -4
    dand at ddchosting.com
    18 years ago
    When I was working on a project I ran into this problem with redirecting. My solution is as follows:
    header("Refresh: 5; url=../main/main.php?".session_id()."");

    This allowed me to pass the session_id() which is used throughout site to make sure user has loged in.
    I hope this helps!
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    -5
    metator at netcabo dot pt
    19 years ago
    Regarding samuele's note:

    You can get faster code if you apply directly what happens in  network devices, such as routers. If you AND (logic operation) the remote ip against the local netmask the result will be the network ip if the remote ip is from the local network. Example:

        192.168.0.16 = 11000000.10101000.00000000.00010000
    & 255.255.255.0 = 11111111.11111111.11111111.00000000
    --------------------------------------------------------------
       192.168.0.0 = 11000000.10101000.00000000.00000000

    And now the code. My example uses a html form where you place the values you want to test:

    <HTML><HEAD><TITLE>Check IP</TITLE>
    </HEAD><BODY>
        <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="POST">

    Hope you find this useful.
            IP to check: <input type="text" name="ip"> <br>
            Local network ip: <input type="text" name="net"> <br>
            Local netmask: <input type="text" name="mask"> <br>
            <input type="submit" name="check" value="Check it!">
        </form>
        <?php

    /**
    * @param string $ip IP to check in dotted decimal format
    * @param string $net Network IP in dotted decimal format
    * @param string $mask Netmask in dotted decimal format
    * @returns true if the ip belongs to the network, false otherwise
    **/
    function isIPIn($ip, $net, $mask) {
            //doesn't check for the return value of ip2long
            $ip = ip2long($_POST['ip']);
            $rede = ip2long($_POST['net']);
            $mask = ip2long($_POST['mask']);
       
            //AND
            $res = $ip & $mask;
       
        return (    $res == $rede);
    }

    if (isset(    $_POST['check'])) {
         echo     isIPIn($_POST['ip'], $_POST['net'], $_POST['mask']) ? "IP IN.": "IP OUT.";
    }
    ?>
    </BODY><HTML>
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    -6
    anderson at piq dot com dot br
    21 years ago
    If you want to get the interface of an IP, based on the local route table, use this.

    function GetIfaceforIP($user_ip)
    {
        $route = "/bin/netstat -rn";

        exec($route, $aoutput);
        foreach($aoutput as $key => $line)
        {
            if($key > 1)
            {
                $line = ereg_replace("[[:space:]]+",",",$line);
                list($network, $gateway, $mask, $flags, $mss, $window, $irtt, $iface) = explode(",", $line)
                if((ip2long($user_ip) & ip2long($mask)) == ip2long($network))
                {
                    return $iface;
                }
            }
        }
    }
    up
    -8
    trevor-hemsley at nospam dot dial dot pipex dot com
    22 years ago
    Previous example of IP range to CIDR list does not cope with ranges as well as the perl Net::Netmask range2cidrlist() function. In PHP this looks like

    <?
    function imask($this)
    {
    // use base_convert not dechex because dechex is broken and returns 0x80000000 instead of 0xffffffff
    return base_convert((pow(2,32) - pow(2, (32-$this)))), 10, 16);
    }

    function     imaxblock($ibase, $tbit)
    {
    while (    $tbit > 0)
    {
    $im = hexdec(imask($tbit-1));
    $imand = $ibase & $im;
    if (    $imand != $ibase)
    {
    break;
    }
    $tbit--;
    }
    return     $tbit;
    }

    function     range2cidrlist($istart, $iend)
    {
    // this function returns an array of cidr lists that map the range given
    $s = explode(".", $istart);
    // PHP ip2long does not handle leading zeros on IP addresses! 172.016 comes back as 172.14, seems to be treated as octal!
    $start = "";
    $dot = "";
    while (list(    $key,$val) = each($s))
    {
    $start = sprintf("%s%s%d",$start,$dot,$val);
    $dot = ".";
    }
    $end = "";
    $dot = "";
    $e = explode(".",$iend);
    while (list(    $key,$val) = each($e))
    {
    $end = sprintf("%s%s%d",$end,$dot,$val);
    $dot = ".";
    }
    $start = ip2long($start);
    $end = ip2long($end);
    $result = array();
    while (    $end > $start)
    {
    $maxsize = imaxblock($start,32);
    $x = log($end - $start + 1)/log(2);
    $maxdiff = floor(32 - floor($x));
    $ip = long2ip($start);
    if (    $maxsize < $maxdiff)
    {
    $maxsize = $maxdiff;
    }
    array_push($result,"$ip/$maxsize");
    $start += pow(2, (32-$maxsize));
    }
    return     $result;
    }
    ?>
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    -8
    philippe-at-cyberabuse.org
    22 years ago
    ... and this one will do the opposite (o return NULL for invalid netblocks) :

    1.0.0.0 1.0.255.255 -> 1.0.0.0/16
    1.0.0.0 1.3.255.255 -> 1.0.0.0/14
    192.168.0.0 192.168.0.255 -> 192.168.0.0/24

    function ip2cidr($ip_start,$ip_end) {
    if(long2ip(ip2long($ip_start))!=$ip_start or long2ip(ip2long($ip_end))!=$ip_end) return NULL;
    $ipl_start=(int)ip2long($ip_start);
    $ipl_end=(int)ip2long($ip_end);
    if($ipl_start>0 && $ipl_end<0) $delta=($ipl_end+4294967296)-$ipl_start;
    else $delta=$ipl_end-$ipl_start;
    $netmask=str_pad(decbin($delta),32,"0","STR_PAD_LEFT");
    if(ip2long($ip_start)==0 && substr_count($netmask,"1")==32) return "0.0.0.0/0";
    if($delta<0 or ($delta>0 && $delta%2==0)) return NULL;
    for($mask=0;$mask<32;$mask++) if($netmask[$mask]==1) break;
    if(substr_count($netmask,"0")!=$mask) return NULL;
    return "$ip_start/$mask";
    }
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