How to display data from database into textbox and update it in PHP?

source code:-

<?php

include('header.php');

include('config.php');

$id=$_REQUEST["id"]; //specify the id when you want to fetch data

 $query="select * from product_master where id=$id";

$data=mysqli_query($conn,$query);

$res=mysqli_fetch_array($data);

$name=$res["product_name"];

$desc=$res["description"];

$image=$res["product_image"];

$cat=$res["category"];

$rate=$res["rate"];

if(isset($_POST["submit"]))

{ 

$file=$_FILES["file"]["name"];

$tmp=$_FILES["file"]["tmp_name"];

$ename=$_POST["name"];

$edesc=$_POST["desc"];

$ecat=$_POST["cat"];

$erate=$_POST["rate"];

$error=0;

if(empty($file))

{

    $msg_file="enter product image";

$error=1;

}

if (empty($ename)) {

$msg_name="enter product name";

$error=1;

}

if (empty($edesc)) {

$msg_desc="enter product description";

$error=1;

}

if (empty($ecat)) {

$msg_cat="enter product category";

$error=1;

}

if (empty($erate)) {

$msg_rate="enter product rate";

$error=1;

}

if($error==0)

{

$folder="image/".$file;

move_uploaded_file($tmp,$folder);

echo $query="update product_master set product_name='$ename',description='$edesc',category='$ecat',rate=$erate,product_image='$folder' where id=$id";

     $data=mysqli_query($conn,$query);

     if($data)

     {

      $msg="update record successfully";

      header('location:index.php');

     }

     else

     {

      $msg="not updated";

     }

}

}

?>

<style type="text/css">

.msg{

  margin-left:20px;

  padding:5px;

  font-size: 14px;

  color: green;

}

</style>

<h1> edit product details</h1>

<div class="msg">

<?php if(isset($msg)){ echo $msg;}  ?>

</div>

<form  method="post" enctype="multipart/form-data">

<div class="input-box">

<label>product name</label>

<input type="text" class="input"name="name" id="name"placeholder="enter prduct name" value="<?php if(isset($name)){ echo $name; }?>">

<label class="msg"><?php if(isset($msg_name)){ echo $msg_name;}  ?></label>

</div>

<div class="input-box">

<label>product description</label>

<textarea class="input" name="desc"><?php if(isset($desc)){ echo $desc; }?></textarea>

<label class="msg"><?php if(isset($msg_desc)){ echo $msg_desc;}  ?></label>

</div>

<div class="input-box">

<label> category</label>

<select name="cat">

<option value="milk">milk</option>

<option value="rice">rice</option>

<option value="wheat">wheat</option>

</select>

<label class="msg"><?php if(isset($msg_cat)){ echo $msg_cat;}  ?></label>

</div>

<div class="input-box">

<label>product image</label>

<input type="file" name="file" id="name" value="<?php if(isset($name)){ echo $name; }?>">

<label class="msg"><?php if(isset($msg_file)){ echo $msg_file;}  ?></label>

</div>

<div class="input-box">

<label>product rate</label>

<input type="text" class="input"name="rate" id="name" value="<?php if(isset($rate)){ echo $rate; }?>">

<label class="msg"><?php if(isset($msg_rate)){ echo $msg_rate;}  ?></label>

</div>

<div class="input-box">

<button type="submit" class="btn btn-primary" name="submit">update </button>

</div>

</form>

</body>

</html>