Use Yii rule validation to change attribute name if form attribute value is empty

I have a model that extends the Yii CFormModel and I would like to define a validation rule that checks whether the attribute value is empty and - if that is the case - sets the attribute name to an empty string instead of changing the input value.

Is such a scenario even possible or are validation rules only intended for warnings and/or changes of the input values?

Any help would be much appreciated.

Below is the example code of my model:

class LoginForm extends CFormModel
{
    public $firstName;
    public $lastName;

    public function rules()
    {
        return array(
            array('firstName, lastName', 'checkIfEmpty', 'changeAttributeName'),
        );
    }
    // some functions
}

Not sure whether your use case is very elegant, but the following should work:

class LoginForm extends CFormModel
{
    public $firstName;
    public $lastName;

    public function rules()
    {
        return array(
            array('firstName, lastName', 'checkIfEmpty'),
        );
    }

    public function checkIfEmpty($attribute, $params) 
    {
        if(empty($this->$attribute)) {
            unset($this->$attribute);
        }
    }

    // some functions
}

Based on hamed's reply, another way would be to use the beforeValidate() function:

class LoginForm extends CFormModel
{
    public $firstName;
    public $lastName;

    protected function beforeValidate()
    {
        if(parent::beforeValidate()) {
            foreach(array('firstName, lastName') as $attribute) {
                if(empty($this->$attribute)) {
                    unset($this->$attribute);
                }
            }
        }
    }

}