Joomla 2.5+：在同一控制器调用中创建帐户并登录

我已使用用户注册创建了一个from。在控制器内处理表单时，我希望用户在之后登录。帐户创建工作正常，但之后登录失败：

function processForm($username,$first_name,$last_name,$email,$password,$groups) {
    jimport('joomla.user.helper');
    $app     = JFactory::getApplication('site');
    $user     = new JUser();

    $b= array();
    $user->bind($b);
    $user->username = $username;
    $user->name     = $first_name." ".$last_name;
    $user->set('id',0);

    $date =date("Y-m-d H:i:s");
    $user->set('registerDate', $date);
    $user->email = $email;
    $user->set('password',JUserHelper::getCryptedPassword($password,JUserHelper::getSalt()));
    $user->set('block', '0');
    $user->save();

    foreach ($groups as $group) {
        JUserHelper::addUserToGroup($user->id, $group);
    }
    $app->login(array("username"=>$username,"password"=>$password));
}

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有什么想法吗？

$session=JFactory:：getSession$会话->设置'user'，$user；可以代替$app->loginarrayusername=>$username，password=>$password；