I have followed this tutorial: <http://www.phpjabbers.com/how-to-make-a-php-calendar-php26-6.html#comments> to make a very basic calendar. My aim is to create a very basic availability calendar whereby booked days are filled in with a different color. I have managed to accomplish this however I would like to be able to indicate mornings and afternoons by filling only half of a squares background color like the following:

<http://www.phpjabbers.com/availability-calendar/>

Does anyone know how I could accomplish this?