grid\DataColumn $format

In which format should the value of each data model be displayed as (e.g. "raw", "text", "html", ['date', 'php:Y-m-d']). Supported formats are determined by the formatter used by the yii\grid\GridView. Default format is "text" which will format the value as an HTML-encoded plain text when yii\i18n\Formatter is used as the formatter of the GridView.