Unlimited file size limit PHP download

gistfile1.php

function readfile_chunked ($filename) { 
  $chunksize = 1*(1024*1024); // how many bytes per chunk 
  $buffer = ''; 
  $handle = fopen($filename, 'rb'); 
  if ($handle === false) { 
    return false; 
  } 
  while (!feof($handle)) { 
    $buffer = fread($handle, $chunksize); 
    print $buffer; 
  } 
  return fclose($handle); 
}