Trim Function in Yii Model

From my sourcecode, I gave the information for trim function in yii framework. When we update the record, This function will apply to all fields.


<?php
class User extends CActiveRecord
{
    public static function model($className=__CLASS__)
    {
        return parent::model($className);
    }
	
    public function tableName()
    {
        return 'tbl_user';
    }
	
    public function rules()
    {
        array('username, password, firstname, lastname, email, address', 
            'filter', 'filter'=>'trim'),
    }
}
?>