php using PEL manipulate the exif data

create.exif.php

<?php

error_reporting(E_ALL);

$root_path = dirname(__FILE__);
$lib_path = $root_path . "/lib/";

include_once($lib_path . 'PelJpeg.php');
include_once($lib_path . 'PelTag.php');
include_once($lib_path . 'PelIfd.php');
include_once($lib_path . 'PelDataWindow.php');

$im = imagecreate(1200, 800);

// create PelJpeg object from gd resource, or filename
$jpeg = new PelJpeg($im);

// create PelExif object
$exif = new PelExif();

// bind the PelExif object to PelJpeg
$jpeg->setExif($exif);

// crate PelTiff object
$tiff = new PelTiff();

// the exif info is actually stored in PelTiff
$exif->setTiff($tiff);

// create IFD tag and add entry
$ifd0 = new PelIfd(PelIfd::IFD0);
$tiff->setIfd($ifd0);
$ifd0->addEntry(new PelEntryAscii(PelTag::IMAGE_DESCRIPTION, "hello world!!!"));

// output the file
file_put_contents("new.jpg", $jpeg->getBytes());

// read back and check
$exif = exif_read_data("new.jpg");

var_dump($exif);

/*

sample output

array(9) {
  ["FileName"]=>
  string(7) "new.jpg"
  ["FileDateTime"]=>
  int(1351572944)
  ["FileSize"]=>
  int(15739)
  ["FileType"]=>
  int(2)
  ["MimeType"]=>
  string(10) "image/jpeg"
  ["SectionsFound"]=>
  string(22) "ANY_TAG, IFD0, COMMENT"
  ["COMPUTED"]=>
  array(5) {
    ["html"]=>
    string(25) "width="1200" height="800""
    ["Height"]=>
    int(800)
    ["Width"]=>
    int(1200)
    ["IsColor"]=>
    int(1)
    ["ByteOrderMotorola"]=>
    int(0)
  }
  ["ImageDescription"]=>
  string(14) "hello world!!!"
  ["COMMENT"]=>
  array(1) {
    [0]=>
    string(57) "CREATOR: gd-jpeg v1.0 (using IJG JPEG v80), quality = 75
"
  }
}
*/