Hi, I'm trying to migrate one of my PHP projects to Doctrine. I've never used it before so there are a few things I don't understand. In my current code, I have a class similar to this:

class ScheduleItem {
   private Date start; //A PEAR Date object.
   private Date end;

   public function getStart() { return $this->start; }
   public function setStart($val) { $this->start = $val; }

   public function getEnd() { return $this->end; }
   public function setEnd($val) { $this->end= $val; }
}

I have a ScheduleItemDAO class with methods like save(), getByID(), etc. When loading from and saving to the database, the DAO class converts the Date objects to and from strings so they can be stored in a timestamp field.

In my attempt to move to Doctrine, I created a new class like this:

class ScheduleItem extends Doctrine_Record {
   public function setTableDefinition() {
      $this->hasColumn('start', 'timestamp');
      $this->hasColumn('end', 'timestamp');
   }
}

I had hoped I would be able to use Date objects for the start and end times, and have them converted to strings when they are saved to the database. How can I accomplish this?