By default, the expression Yii::app()->user returns a [CWebUser] [application component](http://www.yiiframework.com/doc/guide/basics.application#application-component) which represents the information that are closely related with the current user. Some information can be persistent throughout the current user session. For example, [CWebUser] already comes with a [name|CWebUser::name] property that stores the username of the current user.

In order to store more information, we need to modify the [identity|CUserIdentity] class used together with [CWebUser]. Each application may have one or several identity classes which are mainly responsible to provide ways of performing user authentication.

Here we use the UserIdentity class included in the testdrive application as an example, assuming our goal is to add the ID and the last login time of the user to [CWebUser]. We would modify UserIdentity as follows,

class UserIdentity extends CUserIdentity
{
	private $_id;
	
	public function authenticate()
	{
		$user=User::model()->findByAttributes(array('username'=>$this->username));
		if($user===null)
			$this->errorCode=self::ERROR_USERNAME_INVALID;
		else if($user->password!==md5($this->password))
			$this->errorCode=self::ERROR_PASSWORD_INVALID;
		else
		{
			$this->_id=$user->id;
			$this->setState('lastLoginTime', $user->lastLoginTime);
			$this->errorCode=self::ERROR_NONE;
		}
		return !$this->errorCode;
	}
	
	public function getId()
	{
		return $this->_id;
	}
}

In the above, during authentication we retrieve the ID and the last login time information of the authenticated user. We save the ID in a private variable $_id and save lastLoginTime in a state by calling setState(). The reason that we use different approaches to save id and lastLoginTime is because id is a pre-defined property that is recognized by [CWebUser]. If we want to store more information, we should use setState(), like we do with lastLoginTime.

We also override the getId() method to return the private variable $_id. The parent implementation is to return the username.

That's all we need. Now if we want to retrieve the id or lastLoginTime information in our code, we can do the following:

$id=Yii::app()->user->id;
$lastLoginTime=Yii::app()->user->lastLoginTime;

Note: When cookie-based authentication is enabled (by setting [CWebUser::allowAutoLogin] to be true), these persistent information will be stored in cookie. Therefore, you should NOT store sensitive information (e.g. password) like we do in the above.

Related article
The method explained above stores the user data into session or cookies when the user authenticates, there is another method of retrieveing user information from database directly:
Add information to Yii::app()->user by extending CWebUser