无法使用php获取用于更新记录的数据

Question

Trying to update a record unable to fetch the data from database.Getting a blank page not getting any data from database.

<?php
include 'includes/db.php';
$id = (int)$_GET['appoint_id'];
$sql = "SELECT * FROM appointment WHERE appoint_id = '$id'";
$run = mysqli_query($conn,$sql);
while ($row = mysqli_fetch_assoc($run)){
    $firstname = $row['first_name'];
    $lastname = $row['last_name'];        
}   
?>

<form class="form-horizontal" action="update.php" method="post" role="form">
    <input  type='hidden' value='<?=$id;?>' name='appoint_id'>
    <div class="body">
        <div class="row clearfix">
            <div class="col-sm-6 col-xs-12">
                <div class="form-group">
                    <div class="form-line">
                        <input type="text" class="form-control" value="<?php echo $row['first_name'];?>" name="first_name" id="first_name" required>
                    </div>
                </div>
            </div>
            <div class="col-sm-6 col-xs-12">
                <div class="form-group">
                    <div class="form-line">
                        <input type="text" class="form-control" value="<?php echo $row['last_name'];?>" name="last_name" id="last_name" required>
                    </div>
                </div>
            </div>
        </div>
    </div>
</form>

update.php

<?php include 'includes/db.php';
if(isset($_POST['submit_user'])){
        $ins_sql = "UPDATE first_name,last_name appointment  WHERE appoint_id = '$id' ";
        $run_sql = mysqli_query($conn,$ins_sql);
    }else {
        echo "not updated";
    }
 ?>

Not displaying any errors in error log as well.

Answer 1

?php session_start();
include 'includes/db.php';  
$id = (int)$_GET['id'];
$sql = "SELECT * FROM appointment WHERE appoint_id = $id";
$oppointArr =array();
$result = mysqli_query($conn,$sql);
if (mysqli_num_rows($result) > 0) {

  while($row = mysqli_fetch_array($result)) {          
       $oppointArr = $row;
       echo "Name: " . $row["first_name"]. "<br>";
      }
  } else {
  echo "0 results";
 }
//mysqli_close($conn);
 ?>

Query for fetching the data for a particular record