use FacebookFacebookSession;
                use FacebookFacebookRedirectLoginHelper;
                use FacebookFacebookRequest;
                use FacebookFacebookResponse;
                use FacebookFacebookSDKException;
                use FacebookFacebookRequestException;
                use FacebookFacebookAuthorizationException;
                use FacebookGraphObject;
                use FacebookEntitiesAccessToken;
                use FacebookHttpClientsFacebookCurlHttpClient;
                use FacebookHttpClientsFacebookHttpable;

                // start session

                // init app with app id and secret
                FacebookSession::setDefaultApplication('1450546748547040','4c0b36c770bc22bdc45b40bd4c7b7229' );

                // login helper with redirect_uri

                    $helper = new FacebookRedirectLoginHelper('http://www.immomix.ma/mysdk/src/begin.php' );

                try {
                  $session = $helper->getSessionFromRedirect();
                } catch( FacebookRequestException $ex ) {
                  // When Facebook returns an error
                } catch( Exception $ex ) {
                  // When validation fails or other local issues
                }