Ví dụ kiểu submit thiếu value Code: <!DOCTYPE html> <html> <body> <form action="/demo/action_page.php"> Họ:<br> <input type="text" name="firstname" value="Nguyen"> <br> Tên:<br> <input type="text" name="lastname" value="A"> <br><br> <input type="submit"> </form> </body> </html> Kết quả: