Grid/Grid.php
public function showColumns($columnIds)
    {
        foreach ((array) $columnIds as $columnId) {
            $this->lazyHideShowColumns[$columnId] = true;
        }

        return $this;
    }
public function showColumns($columnIds)
    {
        foreach ((array) $columnIds as $columnId) {
            $this->lazyHideShowColumns[$columnId] = true;
        }

        return $this;
    }
Sets on the visibility of columns.

@param string|array $columnIds

@return self