annotations.php

<?php
/**
 * Get the TwitterOAuth source code:
 * http://github.com/abraham/twitteroauth
 * git clone git@github.com:abraham/twitteroauth.git
 *
 * Get your OAuth credentials:
 * http://dev.twitter.com/pages/oauth_single_token
 */

require_once('twitteroauth/twitteroauth.php');

echo '<pre>';

$connection = new TwitterOAuth('consumer key', 'consumer secret', 'access token', 'access token secret');

$annotations = array('foo' => array('bar' => 'baz'));

$result = $connection->post('statuses/update', array( 'status' => 'Hello annotated world!',
                                                    'annotations' => json_encode($annotations)));
if (200 == $connection->http_code) {
  echo 'Success! :)';
} else {
  echo 'Failure! :(';
}

echo '<br><br>';
print_r($result);