Failed to open stream autoload.php Facebook SDK v4

I'm trying to upgrade my app from PHP SDK v2.0 to latest PHP SDK v4. My current version of PHP is 5.4. I've upload the PHP SDK to www/games/facebook/client. I get the following message in the php_error.log:

 PHP Warning:  require(facebook-php-sdk-v4/autoload.php): failed to open stream: No such file or directory in /files/www/games/facebook/classes/RedSocialCore/wrappers/FacebookWrapper.php on line 16

PHP Fatal error:  require(): Failed opening required 'facebook-php-sdk-v4/autoload.php' (include_path='.:/usr/share/php:/usr/share/pear') in /files/www/games/facebook/classes/RedSocialCore/wrappers/FacebookWrapper.php on line 16

This is the initialization:

define('FACEBOOK_SDK_V4_SRC_DIR', 'www/games/facebook/client/facebook-php-sdk-v4/src/Facebook/');
require ('facebook-php-sdk-v4/autoload.php');

use Facebook\FacebookSession;
use Facebook\FacebookJavaScriptLoginHelper;
use Facebook\FacebookRequest;
use Facebook\GraphUser;
use Facebook\FacebookRequestException;

I'll appreciate any advice