Generate 128M file for download testing without using 128M of space

nofile.php

<?php
header('Last-Modified: '.gmdate('D, d M Y H:i:s', time()).' GMT');
header('Expires: '.gmdate('D, d M Y H:i:s', 0).' GMT');
header('Cache-Control: private, no-store, no-cache, must-revalidate, post-check=0, pre-check=0, FALSE');
header('Pragma: no-cache');
header('Content-Disposition: attachment; filename="test.file"');
header('Content-type: application/octet-stream');
header('Content-Length: 134217728');
flush();

$s='0';

// 128k block
for($i = 0 ; $i < 17 ; $i++)
{
  $s .= $s;
}

// 128M output
for($i = 0 ; $i < 1024 ; $i++)
{
  echo $s;
  flush();
}
?>