ObjectMeta::rules PHP Method

    public function rules()
    {
        // NOTE: you should only define rules for those attributes that
        // will receive user inputs.
        return array(array('meta_object_id', 'length', 'max' => 20), array('meta_key', 'length', 'max' => 255), array('meta_value', 'safe'), array('meta_id, meta_object_id, meta_key, meta_value', 'safe', 'on' => 'search'));
    }