yii 查询的数据库结果用print_r打印出来分析求助 [ 未指定版本 ]

yii 查询的结果用print_r打印出来说这个样子，除了需要的字段和对应数据信息 外，其他是什么意思，有什么作用？
Array
(
    [0] => Category Object
        (
            [_new:CActiveRecord:private] => 
            [_attributes:CActiveRecord:private] => Array
                (
                    [catid] => 19
                    [type] => 2
                    [modelid] => 0
                    [catname] => 首页
                    [url] => /index.php
                    [catdir] => 
                )

            [_related:CActiveRecord:private] => Array
                (
                )

            [_c:CActiveRecord:private] => 
            [_pk:CActiveRecord:private] => 19
            [_alias:CActiveRecord:private] => t
            [_errors:CModel:private] => Array
                (
                )

            [_validators:CModel:private] => 
            [_scenario:CModel:private] => update
            [_e:CComponent:private] => 
            [_m:CComponent:private] => 
        )