php update not changing in database

<?php include 'database/db.php'; 

if(isset($_POST['insertdata'])){

    $id = $_POST['id'];

    $fname = $_POST['fname'];
    $mname = $_POST['mname'];
    $lname = $_POST['lname'];
    $dbirth = $_POST['dbirth'];
    $email = $_POST['email'];
    $address = $_POST['address'];
    $number = $_POST['number'];
    $civil = $_POST['civil'];
    $gender = $_POST['gender'];
    $hobbies = $_POST['hobbies'];

    $sql = "UPDATE crud_activity_tb  SET fname='$fname', mname='$mname', lname='$lname', dbirth='$dbirth', email='$email', address='$address',
    number='$number', civil='$civil', gender='$gender', hobbies='$hobbies' WHERE id = '$id' ";
    $query_run = mysqli_query($conn, $sql);

    if($query_run){
        echo'<script>alert("data update");</script>';
        header('Location: index.php');
    }
    else{
        echo '<script>alert("data not save");</script>';
    }

}

?>

the data are not changing but there is no error.. please help me