Twitpic-Flickr bridge. Now I can upload photos to Flickr via my iPhone Twitter app, yay!

twitpic_flickr.php

<?PHP

# Twitpic-Flickr bridge - v0.1pre - 10/18/2011
# http://benalman.com/
# 
# Copyright (c) 2011 "Cowboy" Ben Alman
# Dual licensed under the MIT and GPL licenses.
# http://benalman.com/about/license/

# There's no way I'm writing all the Flickr stuff myself.
# http://phpflickr.com/
require_once('phpFlickr/phpFlickr.php');

# Create an app: http://www.flickr.com/services/apps/create/apply/
# Edit your app flow: http://www.flickr.com/services/apps/YOUR_APP_ID/auth/
# * Check "Web application"
# * Callback URL needs to be the URL of this PHP script.

# Fill in these values: http://www.flickr.com/services/apps/YOUR_APP_ID/key/
$apikey = 'YOUR_API_KEY';
$secret = 'YOUR_SECRET';
$f = new phpFlickr($apikey, $secret);

# You might need to create this file and set it to be writable. Is a file even
# necessary? Can twitter apps store this token in a session?
$tokenfile = 'twitpic_flickr_token.txt';
if (file_exists($tokenfile)) {
  $token = file_get_contents($tokenfile);
}

if ($_GET['frob']) {
  # Token passed from Flickr, store it in the token file and exit. Does this
  # have to exit here? Can it continue on?
  $token_obj = $f->auth_getToken($_GET['frob']);
  $token = $token_obj['token'];
  file_put_contents($tokenfile, $token);
  exit();
} elseif ($token == '') {
  # No token, request one from Flickr.
  $f->auth('write');
}

# Set the token to enable uploading.
$f->setToken($token);

# Customize these as-needed.
$source = 'Cowboy!';
$description = '(posted to twitter)';
$tags = 'flickr iphone';

# Upload photo to Flickr.
$message = $_POST['message'];
$media = $_FILES['media']['tmp_name'];
$photoid = $f->sync_upload($media, $message, $description, $tags, 1);

# The Flickr URL shortening service expects a base58-encoded photo id.
# This function was borrowed from http://gul.ly/d50
function base58_encode($num) {
  $alphabet = '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ';
  $base_count = strlen($alphabet);
  $encoded = '';

  while ($num >= $base_count) {
    $div = $num / $base_count;
    $mod = ($num - ($base_count * intval($div)));
    $encoded = $alphabet[$mod] . $encoded;
    $num = intval($div);
  }

  if ($num) {
    $encoded = $alphabet[$num] . $encoded;
  }

  return $encoded;
}

if ($photoid) {
  $url = 'http://flic.kr/p/' . base58_encode($photoid);
} else {
  $url = '';
}

# Write out the Flickr URL.
?><mediaurl><?= $url ?></mediaurl>