how to use keys in ArrayDataProvider




yii\data\ArrayDataProvider Object

(

    [key] => 

    [allModels] => Array

        (

            [0] => Array

                (

                    [prg_id] => 7

                    [emp_id] => 7496

                )


            [1] => Array

                (

                    [prg_id] => 7

                    [emp_id] => 3021

                )


            [2] => Array

                (

                    [prg_id] => 7

                    [emp_id] => 13076

                )


        )


    [modelClass] => 

    [id] => 

    [_sort:yii\data\BaseDataProvider:private] => 

    [_pagination:yii\data\BaseDataProvider:private] => yii\data\Pagination Object

        (

            [pageParam] => page

            [pageSizeParam] => per-page

            [forcePageParam] => 1

            [route] => 

            [params] => 

            [urlManager] => 

            [validatePage] => 1

            [totalCount] => 0

            [defaultPageSize] => 20

            [pageSizeLimit] => Array

                (

                    [0] => 1

                    [1] => 50

                )


            [_pageSize:yii\data\Pagination:private] => 20

            [_page:yii\data\Pagination:private] => 

        )


    [_keys:yii\data\BaseDataProvider:private] => Array

        (

            [0] => prg_id

            [1] => emp_id

        )


    [_models:yii\data\BaseDataProvider:private] => 

    [_totalCount:yii\data\BaseDataProvider:private] => 

    [_events:yii\base\Component:private] => Array

        (

        )


    [_behaviors:yii\base\Component:private] => 

)



but i am getting this error.

7143

errors.png

Your "keys" property is set incorrectly:

http://www.yiiframework.com/doc-2.0/yii-data-basedataprovider.html#$keys-detail