0 && in_array($answer, ['A', 'B', 'C', 'D'])) { $stmt = $conn->prepare("INSERT INTO student_answers (user_id, question_id, answer) VALUES (?, ?, ?) ON DUPLICATE KEY UPDATE answer = VALUES(answer)"); if ($stmt) { $stmt->bind_param("iis", $user_id, $question_id, $answer); $stmt->execute(); } } echo "OK";