grid\Column $contentOptions

The HTML attributes for the data cell tag. This can either be an array of attributes or an anonymous function (Closure) that returns such an array. The signature of the function should be the following: function ($model, $key, $index, $column). Where $model, $key, and $index refer to the model, key and index of the row currently being rendered and $column is a reference to the yii\grid\Column object. A function may be used to assign different attributes to different rows based on the data in that row.

See also yii\helpers\Html::renderTagAttributes() for details on how attributes are being rendered.