This class provides a simple interface for OAuth 2.0.

- OAuth 2.0 draft 12 supported (default mode: draft 10) .
- The library requires PHP >= 5.3.
- The http request engine depends on the PHP stream or curl extension with SSL/TLS.
- A fallback mode for ealier draft version of OAuth 2.0 supported.
  (for Facebook)
- the file upload can be detected if the leading char of value is '@'.
- MAC, BEARER Authorization header supported.

 @author Rui Hirokawa <rui_hirokawa at yahoo.co.jp>
 @copyright Copyright (c) 2011, Rui Hirokawa
 @license http://www.opensource.org/licenses/mit-license.php MIT

Usage:

<code>
   // for Facebook OAuth 2.0
   $url = "https://graph.facebook.com/me/feed";

   $entry = array('callback'=>'http://www.example.com/ws_fb.php',
   'authorize'=>'https://graph.facebook.com/oauth/authorize',
   'access_token'=>'https://graph.facebook.com/oauth/access_token');

   $opts = array('redirect_uri'=>$entry['callback'],
   'scope'=>'read_stream,offline_access,publish_stream');

   $copts = array('cainfo'=>CAFILE); // can be ignored if cainfo available
   $oauth = new LightOAuth2(CLIENT_ID, CLIENT_SECRET, $copts);
   
   session_start();
   if (!isset($_SESSION['access_token'])) {
    if (!isset($_GET['code'])) {
      $url = $oauth->getAuthUrl($entry['authorize'], $entry['callback'], $opts);
      header("Location: " . $url);
      exit();
    }
    $obj = $oauth->getToken($entry['access_token'], $entry['callback'],
                           $_GET['code'], 'json');
    $_SESSION['access_token'] = $obj->access_token;
   }

   // access to proteced resource
   $oauth->setToken($_SESSION['access_token']);
   $response = $oauth->fetch($url);
</code>