public function login($username = null, $password = null)
{
if (!isset($username) && isset($_POST['username'])) {
$username = $_POST['username'];
}
if (!isset($password) && isset($_POST['password'])) {
$password = $_POST['password'];
}
$result = $this->request('POST', 'login', compact('username', 'password'));
$this->userinfo = $result;
return $this->userinfo;
}