<?php

    function checkATT() {
        $ipaddy = $_SERVER['REMOTE_ADDR'];
        /*echo $ipaddy;
        echo ip_in_range($ipaddy, '12.20.0.0/8');
        echo ip_in_range($ipaddy, '76.192.0.0/10');
        echo ip_in_range($ipaddy, '68.88.0.0/13');
        echo ip_in_range($ipaddy, '75.0.0.0/10');
        echo ip_in_range($ipaddy, '99.128.0.0/10'); */
        if (ip_in_range($ipaddy, '209.0.0.0/10') ||ip_in_range($ipaddy, '99.128.0.0/10') || ip_in_range($ipaddy, '75.0.0.0/10') || ip_in_range($ipaddy, '68.88.0.0/13') ||  ip_in_range($ipaddy, '76.192.0.0/10') || ip_in_range($ipaddy, '12.20.0.0/8')) {
            echo 'Link to informative article or redirect to same.';
        } else {
            echo '<!-- Probably nothing here, to not bother non-ATT customers. -->';
        }

    }

    /*
     * ip_in_range.php - Function to determine if an IP is located in a
     *                   specific range as specified via several alternative
     *                   formats.
     *
     * Network ranges can be specified as:
     * 1. Wildcard format:     1.2.3.*
     * 2. CIDR format:         1.2.3/24  OR  1.2.3.4/255.255.255.0
     * 3. Start-End IP format: 1.2.3.0-1.2.3.255
     *
     * Return value BOOLEAN : ip_in_range($ip, $range);
     *
     * Copyright 2008: Paul Gregg <pgregg@pgregg.com>
     * 10 January 2008
     * Version: 1.2
     *
     * Source website: http://www.pgregg.com/projects/php/ip_in_range/
     * Version 1.2
     *
     * This software is Donationware - if you feel you have benefited from
     * the use of this tool then please consider a donation. The value of
     * which is entirely left up to your discretion.
     * http://www.pgregg.com/donate/
     *
     * Please do not remove this header, or source attibution from this file.
     */


    // decbin32
    // In order to simplify working with IP addresses (in binary) and their
    // netmasks, it is easier to ensure that the binary strings are padded
    // with zeros out to 32 characters - IP addresses are 32 bit numbers
    Function decbin32 ($dec) {
      return str_pad(decbin($dec), 32, '0', STR_PAD_LEFT);
    }

    // ip_in_range
    // This function takes 2 arguments, an IP address and a "range" in several
    // different formats.
    // Network ranges can be specified as:
    // 1. Wildcard format:     1.2.3.*
    // 2. CIDR format:         1.2.3/24  OR  1.2.3.4/255.255.255.0
    // 3. Start-End IP format: 1.2.3.0-1.2.3.255
    // The function will return true if the supplied IP is within the range.
    // Note little validation is done on the range inputs - it expects you to
    // use one of the above 3 formats.
    Function ip_in_range($ip, $range) {
      if (strpos($range, '/') !== false) {
        // $range is in IP/NETMASK format
        list($range, $netmask) = explode('/', $range, 2);
        if (strpos($netmask, '.') !== false) {
          // $netmask is a 255.255.0.0 format
          $netmask = str_replace('*', '0', $netmask);
          $netmask_dec = ip2long($netmask);
          return ( (ip2long($ip) & $netmask_dec) == (ip2long($range) & $netmask_dec) );
        } else {
          // $netmask is a CIDR size block
          // fix the range argument
          $x = explode('.', $range);
          while(count($x)<4) $x[] = '0';
          list($a,$b,$c,$d) = $x;
          $range = sprintf("%u.%u.%u.%u", empty($a)?'0':$a, empty($b)?'0':$b,empty($c)?'0':$c,empty($d)?'0':$d);
          $range_dec = ip2long($range);
          $ip_dec = ip2long($ip);

          # Strategy 1 - Create the netmask with 'netmask' 1s and then fill it to 32 with 0s
          #$netmask_dec = bindec(str_pad('', $netmask, '1') . str_pad('', 32-$netmask, '0'));

          # Strategy 2 - Use math to create it
          $wildcard_dec = pow(2, (32-$netmask)) - 1;
          $netmask_dec = ~ $wildcard_dec;

          return (($ip_dec & $netmask_dec) == ($range_dec & $netmask_dec));
        }
      } else {
        // range might be 255.255.*.* or 1.2.3.0-1.2.3.255
        if (strpos($range, '*') !==false) { // a.b.*.* format
          // Just convert to A-B format by setting * to 0 for A and 255 for B
          $lower = str_replace('*', '0', $range);
          $upper = str_replace('*', '255', $range);
          $range = "$lower-$upper";
        }

        if (strpos($range, '-')!==false) { // A-B format
          list($lower, $upper) = explode('-', $range, 2);
          $lower_dec = (float)sprintf("%u",ip2long($lower));
          $upper_dec = (float)sprintf("%u",ip2long($upper));
          $ip_dec = (float)sprintf("%u",ip2long($ip));
          return ( ($ip_dec>=$lower_dec) && ($ip_dec<=$upper_dec) );
        }

        echo 'Range argument is not in 1.2.3.4/24 or 1.2.3.4/255.255.255.0 format';
        return false;
      }

    }

    checkATT();