php update code

<?php
ob_start();
require 'connection.php';
session_start();

$id=$_GET['id'];
$question1 = mysqli_real_escape_string($con, $_POST['question']);
$answer1 = mysqli_real_escape_string($con, $_POST['answer']);



$sql = "SELECT * FROM `faq` where id='".$id."'";
$result = mysqli_query($con,$sql);
if(mysqli_num_rows($result)>0)   
    {
        while($row=mysqli_fetch_assoc($result))
            {
                $question=$row["question"];
                $answer=$row["answer"];
            }
    }
   



if(empty($question1))
    {
        $question1=$question;
    }
else
    {
        $question1=$question1;

}


if(empty($answer1))
    {
        $answer1=$answer;
    }
else
    {
        $answer1=$answer1;
    }

 $sql1="UPDATE `faq` set question='".$question1."',answer='".$answer1."' where id='".$id."'";


if(mysqli_query($con,$sql1))
    {
        header("Location:a_view_faq.php");
    }
else
    {
        die('Error:' . mysqli_error($con));
    }

?>