获取最后登录详细信息

I developed login system. It works perfectly. Now I want to get last login date and time and display it. Display part is ok. I tried this code to update logtime field in DB if login success.

$query      =   "SELECT * FROM user WHERE email='$email' AND passwordR='$password' AND status='1' ";

    $result     =   mysqli_query($con,$query)or die(mysqli_error($con));
    $num_row    =   mysqli_num_rows($result);
    $row        =   mysqli_fetch_array($result);

    if( $num_row ==1 ) {
            $_SESSION['user_name']  =   $email;
            $sql="UPDATE user SET logtime = now()";
            mysqli_query($con,$query)or die(mysqli_error($con));
                       }

And my logtime row defined as below,

 `logtime` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,

How ever logtime is not updated.Why is

$sql="UPDATE user SET logtime = now()";

not possible?

That should do the trick.

$sql="UPDATE user SET logtime = now() WHERE email='$email' AND passwordR='$password' AND status='1'";