I have a cube process that displays a classroom schedule. rows are hours and columns are the days. the value is the teacher name:

->pipe(new Cube(array(
            'row' => 'hour_num',
            'column' => 'day',
            'max' => "teacher_name",
        )))

I want to be able to display to different columns in the value like this:

->pipe(new Cube(array(
            'row' => 'hour_num',
            'column' => 'day',
            'max' => "teacher_name, class_name",
        )))

When I write two columns names in the max parameter it shows always the last one.