PHP function to chunk the given IP address range into multiple ranges of given size.

chunkIPRange.php

<?php
/**
* Copyright (C) 2016 Prabhas Gupte
* 
* This is free script: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* 
* This script is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
* 
* You should also see <http://www.gnu.org/licenses/gpl.txt>
*/
function chunkIPRange($ipRange, $numberOfChunks = 2) {
  list($startIP, $endIP) = explode('-', $ipRange);

  $startIPNumeric = ip2long($startIP);
  $endIPNumeric = ip2long($endIP);

  $expandedRange = range($startIPNumeric, $endIPNumeric);
  $size = count($expandedRange);

  $chunkSize = floor($size / $numberOfChunks) + ($size % $numberOfChunks);

  $rangeChunks = array_chunk($expandedRange, $chunkSize);

  $chunkNumber = 0;
  $chunks = array();

  foreach ($rangeChunks as &$chunk) {
    $chunkStart = array_shift($chunk);
    $chunkEnd = array_pop($chunk);

    $chunkStart = long2ip($chunkStart);
    $chunkEnd = long2ip($chunkEnd);

    $chunks[$chunkNumber] = (($chunkStart !== $chunkEnd) && ($chunkEnd !== '0.0.0.0')) ? "$chunkStart-$chunkEnd" : "$chunkStart";
    $chunkNumber++;
  }
  unset($rangeChunks);

  return $chunks;
} // chunkIPRange

print_r(chunkIPRange('10.10.10.1-10.10.20.10', 3));
print_r(chunkIPRange('172.16.0.1-172.16.1.10'));
?>