Mine

<?php

$vars['start']   = $_GET['start'];
$vars['end']     = $_GET['end'];
$vars['charset'] = $_GET['charset'];

if($vars['charset'] == '26') {
  $chars = array('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z');
} else {
  echo "Invalid charset";
  exit;
}

foreach(range(0,8) as $key) {
  foreach(range(1,$key) as $tracker) {
    $intervals[$key] += pow($vars['charset'], $tracker);
  }
}

$intervals[0] = 0;

echo "<pre>";
print_r($vars);
print_r($intervals);
echo "</pre>";

function find_max_length($end) {
  global $intervals;
  foreach(range(1,sizeof($intervals)) as $cnt) {
    if($end > $intervals[$cnt - 1] AND $end <= $intervals[$cnt]) {
      return $cnt;
    }
  }
}

echo $max_length;

function make_string($num) {
  global $vars, $chars;
  
  $max_length = find_max_length($vars['end']);
  
  foreach(range(0,$max_length) as $cnt) {
    $temp[$cnt] = floor($num / $vars['charset']) - 1;
    // I need to finish the math, this is where I am stuck..trying to figure out
    // how to deduct the right amount to make it work.

  }

/*
  echo $temp;
    
    $str[0] = $chars[$temp];
    $str[0] = $chars[$temp];

    $str[1] = $chars[$num - ($temp*$vars['charset'])];

    $string = $str[3].$str[2].$str[1].$str[0];
  
*/

  return $string;
}

foreach(range($vars['start'],$vars['end'] - 1) as $cnt) {
  echo make_string($cnt)."<br />";
}

// For testing
/*
$count = 0;
foreach(range(0,25) as $num1) {
  foreach(range(0,25) as $num2) {
    foreach(range(0,25) as $num3) {
      $count++;
      echo $chars[$num1].$chars[$num2]." ".$count."<br />";
    }
  }
}
*/
?>