function countTextLines($filename) {

  $f = fopen($filename, 'rb');
  $lines = 0;

  while (!feof($f)) {
    $buffer = fread($f, 8192);
    $lines += substr_count($buffer, "\n");
  }

  fclose($f);

  return $lines + (strlen($buffer) ? 1 : 0);
}