php - yii import extension not finding class -

i using facebook sdk php. added facebook php sdk in yii app protected/extension folder , imported in config/main.php follow.

'import' => array(     'application.extensions.facebook.*', ), 

my problem app not finding classes in sdk when create object follows:

 $session = new facebooksession($access_token); 

it giving error follow:

fatal error: class 'facebooksession' not found .... 

if try using include_once() or require_once() giving error below:

fatal error: cannot redeclare class facebook\facebooksession in d:\localhost\protected\extensions\facebook\facebooksession.php on line 36 

what going wrong?

solved adding

set_include_path(yii::app()->baseurl . directory_separator . 'protected' . directory_separator . 'extensions' . directory_separator . 'facebook');

require_once (yii::app()->baseurl . directory_separator . 'protected' . directory_separator . 'extensions' . directory_separator . 'facebook' . directory_separator . 'autoload.php');

require_once (yii::app()->baseurl . directory_separator . 'protected' . directory_separator . 'extensions' . directory_separator . 'facebook' . directory_separator . 'src' . directory_separator . 'facebook' . directory_separator . 'facebooksession.php');

and creating object

$session = new facebook\facebooksession($access_token);