Login yii using last session

hi there;

I want to log with yii using last opend session but always when I close my Navigator I lose last session so I should log again using password and username, I dont know how to retrieve and use last session, like Gmail when I open it in my navigator my session still open entel I close it.

this is my code




class UserIdentity extends CUserIdentity{

public function authenticate(){

        $client=User::model()->findByAttributes(array('username'=>$this->username));

        if(empty($client)) $this->errorCode=self::ERROR_PASSWORD_INVALID;

          else if(!empty($client)){

            if(strcmp(md5($this->password), $client->password)!=0)

                 $this->errorCode=self::ERROR_PASSWORD_INVALID;

            else if(strcmp(md5($this->password), $client->password)==0){

             $this->_id=$client->username;   

             $this->setState('role', 'USER');

             $compte=Comptecabinet::model()->findByPk($client->idcompte); 

             $this->errorCode=self::ERROR_NONE;

             $this->setState('XthisX',$client->idcompte);

			 $this->setState('TimeConnexion',date("Y-m-d H:i"));

        }

   }

}




in model




public function authenticate($attribute,$params)

	{

		if(!$this->hasErrors())

		{

			$this->_identity=new UserIdentity($this->username,$this->password);

			if(!$this->_identity->authenticate())

				$this->addError('password','Incorrect username or password.');

		}

	}

	

	

	public function login()

	{

		if($this->_identity===null)

		{

			$this->_identity=new UserIdentity($this->username,$this->password);

			$this->_identity->authenticate();

		}

		if($this->_identity->errorCode===UserIdentity::ERROR_NONE)

		{

			$duration=$this->rememberMe ? 3600*24*30 : 0; 

			Yii::app()->user->login($this->_identity,$duration);

			return true;

		}

		else

			return false;

	}