Fatal error: Uncaught PDOException: SQLSTATE[23503]: Foreign key violation: 7 ERROR: update or delete on table "classes" violates foreign key constraint "students_class_id_fkey" on table "students" DETAIL: Key (id)=(8) is still referenced from table "students". in /var/www/html/modules/classes/ClassRepository.php:107 Stack trace: #0 /var/www/html/modules/classes/ClassRepository.php(107): PDOStatement->execute(Array) #1 /var/www/html/modules/classes/delete.php(12): App\Modules\Classes\ClassRepository->delete(8) #2 /var/www/html/public/index.php(33): require('/var/www/html/m...') #3 {main} thrown in /var/www/html/modules/classes/ClassRepository.php on line 107