php - user_login_submit() is not working in Drupal 8 with AngularJS -

i working angularjs, rest api & drupal 8. able pass values between angularjs , php, drupal user authentication working, user_login_submit() not working. in console, shows 500 internal server error

please take of code

    if(isset($_post)){     // getting posted data , decodeing json         $_post = json_decode(file_get_contents('php://input'), true);          $username = $_post['username'];         $password = $_post['password'];         $form_state['uid'] = \drupal::service('user.auth')->authenticate($username, $password);          $uid = $form_state['uid'];         if($uid != '' || $uid != null){             $user = user_load($uid);             user_login_submit($form, &$form_state);             return 'successfully logged in';         }         else{             return false;         }  } 

$username = $_post['username']; $password = $_post['password']; 

must be

$username = $_post['name']; $password = $_post['pass']; 

hope works.