public function getExaminees($project_id = null) { if ($project_id) { $exams = Examinee::getAll($project_id); $ans = array(); foreach ($exams as $exam) { $ans[$exam->id] = $exam; } return $ans; } else { if ($this->examinees == null) { $this->examinees = $this->getExaminees($this->project_id); } return $this->examinees; } }