public function __construct(UserService $userService, $username $password)
{
    $this->username = $username;
    $this->password = $password;
    $this->user = $userService->fetchUser($username);
}

public static function checkPassword()
{
    if ($user->password == md5($this->password)) {
        return true;
    } else {
        return false;
    }
}