framework/validators/FilterValidator.php
public function validateAttribute($model, $attribute)
    {
        $value = $model->$attribute;
        if (!$this->skipOnArray || !is_array($value)) {
            $model->$attribute = call_user_func($this->filter, $value);
        }
    }
public function validateAttribute($model, $attribute)
    {
        $value = $model->$attribute;
        if (!$this->skipOnArray || !is_array($value)) {
            $model->$attribute = call_user_func($this->filter, $value);
        }
    }
{@inheritdoc}