public static function addCourse($tutorId, $teachingCoursesId, $termId) { foreach ($teachingCoursesId as $courseId) { Course::validateId($courseId); if (Tutor::teachesCourseWithIdOnTerm($courseId, $tutorId, $termId)) { throw new Exception("Tutor already teaches a course with id {$courseId}"); } } Term::validateId($termId); Tutor_has_course_has_schedule::addCourses($tutorId, $teachingCoursesId, $termId); }