PHP JPEG Progressive Check

<?php
// this code (C) Musicman 2001
// this code is GPL
// feel free to obtain a copy of LICENSE.TXT from
// the Free Software Foundation
// and read up the details

define("MARKER", 0xff);
define("SOI", 0xd8);
define("EOI", 0xd9);
define("JFIF", 0xe0);
define("APP", 0xe0);
define("QUANT", 0xdb);
define("HUFF", 0xc4);
define("SOF0", 0xc0);
define("SOF1", 0xc1);
define("SOF2", 0xc2);
define("SOS", 0xda);
define("ED", 0xed);
define("EE", 0xee);
define("DD", 0xdd);
function u16($fp)
{  $res = ord(fread($fp, 1)) << 8;
  $res += ord(fread($fp, 1));
  return $res;
}
function jpeghdr($fp)
{  if(ord(fread($fp, 1)) != MARKER || ord(fread($fp, 1)) != SOI)
    return false;
  $length = 2;
  $res = false;
  while(ord(fread($fp, 1)) == MARKER)
  {  $cod = ord(fread($fp, 1));
    if($cod == SOS)
      break;
    $len = u16($fp);
    if($cod == QUANT || $cod == HUFF || $cod == DD || $cod == SOF0 || $cod == SOF1)
      $length += 2 + $len;
    if($cod == SOF0 || $cod == SOF1)
    {  $len -= 5;
      $res = array();
      $res["prec"] = ord(fread($fp, 1));
      $res["height"] = u16($fp);
      $res["width"] = u16($fp);
    }  
    else if($cod == SOF2)
      return false;
    else if($cod != JFIF && $cod != QUANT && $cod != HUFF && $cod != DD && ($cod & APP) != APP)
      return false;
    fseek($fp, $len-2, 1);
  }
  if($cod == SOS)
  {  $pos = ftell($fp);
    fseek($fp, 0, 2);
    $length += ftell($fp) - $pos;
    $res['length'] = $length;
    return $res;
  }
  return false;
}
function testjpeg($name)
{  if(!($fp = @fopen($name, "rb")))
    return false;
  $res = jpeghdr($fp);
  fclose($fp);
  return $res;
}

function readjpeg($fp) {  rewind($fp);
  if(ord(fread($fp, 1)) != MARKER || ord(fread($fp, 1)) != SOI)
    return false;
  $buf = chr(MARKER) . chr(SOI);
  while(ord(fread($fp, 1)) == MARKER)
  {  $cod = ord(fread($fp, 1));
    if($cod == SOS)
      break;
    if($cod == QUANT || $cod == HUFF || $cod == DD || $cod == SOF0 || $cod == SOF1)
    {  $len = u16($fp);
      $buf .= chr(MARKER) . chr($cod);
      $buf .= chr($len >> 8);
      $buf .= chr($len & 0xff);
      $buf .= fread($fp, $len-2);
    }
    else
    {  $len = u16($fp);
      fseek($fp, $len-2, 1);
    }
  }
  $buf .= chr(MARKER) . chr($cod);
  while($next = fread($fp, 4096))
    $buf .= $next;
  return $buf;
}

// $pic is a local filename path to the image.
if ($jh = testjpeg($pic)) {
  echo 'good';
} else {
  echo 'Could be saved as progressive - fixing.';

  $imagedata = getimagesize($pic);
  $width = $imagedata[0];
  $height = $imagedata[1];

  $im2 = ImageCreateTrueColor($width, $height);
  $image = ImageCreateFromJpeg($pic);
  imageCopyResampled($im2, $image, 0, 0, 0, 0, $width, $height, $imagedata[0], $imagedata[1]);
  @imagejpeg($im2, $pic);
}