PHP - Last Step, Updating Data In Table...passing Data

<?php

// submit.php 

// STEP 1

// On (LOCAL) SERVER #1 TO relay $variables to 'process.php' on (REMOTE) SERVER #2

// To submit $variables to directly another destination server script
// NOTE: The $variable are NOT the result of Form Input !!!

// For login Authenticaion ALL 3 must match db entries on SERVER #2 
// NOTE: (Again) The $variables are NOT the result of Form Input !!! 

$userid = "adam";
$passwd = "eve";
$pscode = "peterpan";

// NOTE: (Again) The $variable are NOT the result of Form Input !!! 
// These $variables are needed for MySQL db INSERT on the destination URL server
// For testing simplicity (actual data will be 12 $variables)

$a = "apple";
$b = "banana";
$u = "1234567;

//
// Not sure if something called 'CURL' is needed here ???
//

$submit_to_url = http://www.blahblah.com/process.php";

?>

<?php

// processor.php

// STEP 2

// ON SERVER #2 TO RECEIVE DATA DIRECTLY FROM SERVER #1 'submit.php'

// To receive and process the $variables into a MySQL db on SERVER #2
// NOTE: The $variables are NOT the result of Form Input !!!

// First validate $userid, $passwd & $pscode against `verify` table MySQL records

require '/SERVER_2_securelocation_for_database_connection/secret_mysqli.php';

if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

//
// Not sure if something called 'CURL' is needed here ???
//

// These login $variables are from submit.php on SERVER #1

$userid 
$passwd 
$pscode

$sql="SELECT `userid`, `passwd`, `pscode` FROM `verify` 
WHERE `userid` = '$userid'" AND `passwd` = '$passwd` AND `pscode` = '$pscode';

$result = mysqli_query($con,$sql);

if (!mysqli_query($con,$sql)) {
  die('Error: ' . mysqli_error($con));
}

//
// Then some Authentication code if ALL 3 components match
//

// If Authentication = true then $passed = "YES" must sent
// be sent back to the 'finalstep.php' script on SERVER #1
// If Authentication (or connection) = false ... $passed = "NO" 

$return_to_url = http://www.blahblah.com/finalstep.php";

// These $variables are from submit.php on SERVER #1

$a = "apple";
$b = "banana";
$u = "1234567";

$sql="INSERT INTO `data` (`a`, `b`, `u`) 
VALUES ('$a', '$b', '$u')"; 

if (!mysqli_query($con,$sql)) {
  die('Error: ' . mysqli_error($con));
}

// If $SQL INSERT into `data` on SERVER #2 works ...
// $status = "Pending" must be sent back to the 'finalstep.php' 
// script on SERVER #1 for MySQL db Table insertion
// If $SQL INSERT into `data` = false, then $status = "Error"
// NOTE: The '$u' $variable also needs send back to finalstep.php !!!

$return_to_url = http://www.blahblah.com/finalstep.php";

mysqli_close($con);

?>

<?php

// finalstep.php 

// STEP 3

// ON SERVER #1 TO RECEIVE DATA DIRECTLY BACK FROM SERVER #2 process.php

// To receive the $passed, $status and $u $variables for final step action
// NOTE: The $variable are NOT the result of Form Input !!!

require '/SERVER_1_securelocation_for_database_connection/secret_mysqli.php';

if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

// These $variables are from process.php on SERVER #2

$passed
$status
$u

$sql="UPDATE `tracking` 
SET `passed` = '$passed',
    `status` = '$status' 
WHERE `uniqueid` = '$u' ";

$result = mysqli_query($con,$sql);

if (!mysqli_query($con,$sql)) {
  die('Error: ' . mysqli_error($con));
}

mysqli_close($con);

?>

	(function(a){
		a(".history").on("click",function(){

			var b=a(this).data("mp4");
			var store_type=a(this).data("store_type");
			var store_title=a(this).data("store_title");
			var store_tmdbid=a(this).data("store_tmdbid");
			var subtitle=a(this).data("subtitle");
			var resume=a(this).data("resume");
			var user_id=a(this).data("user_id");
			var playpath=a(this).data("mp4")+a(this).data("resume");

			a(".yt-modal-box").append('<div class="modal fade" id="yt-modal"><div class="modal-dialog"><div class="modal-body flex-video widescreen"></div></div></div>');
			a("#yt-modal").modal();
			a("#yt-modal").find(".modal-body").html('<button type="button" class="modal-close" data-dismiss="modal" aria-hidden="true"></button><div id="video_container"><video width="100%" controls autoplay id="video"><source src="'+playpath+'" type="video/mp4"><track kind="subtitles" src="files/Movies/Subtitles/'+subtitle+'" srclang="et" />Your browser does not support the video tag.</video></div>');
			a(document).on("hide.bs.modal",function(){ clearInterval(refreshId); a(".modal-body").html("")})

			function updater(){
				$.post("modules/api/unfinished/update.php",{
					unban: "none",
					user_id: user_id,
					filename: b,
					store_type: store_type,
					store_title: store_title,
					store_tmdbid: store_tmdbid,
					lenght:	video.duration,
					position: video.currentTime,
				})
				.done(function(data){
			    if(data == 1){

						$.post("assets/api/unfinished/update.php",{
							unban: "unban", user_id: user_id, filename: b, lenght:	video.duration, position: video.currentTime,
						})

						function redirect(){
						   window.location = 'logout.php'
						}

						setTimeout(redirect, 2000);

			    }
			  });
			}

			var refreshId = setInterval(updater, 5000);

		})
	})(jQuery);

<video id="example_video_1" class="video-js vjs-default-skin vjs-big-play-centered history" controls preload="auto" width="100%" height="389" data-resume="123" data-setup="{}" >

var myValue;

(function(a){
			
 a(".history").ready(function(){
  myValue=a(this).data("resume");
 })

 videojs("example_video_1").ready(function(){
			
  var myPlayer = this;
		  
  myPlayer.on("play", function(){
   alert(window.myValue);  // I would like to use the myValue under this.
  });
		  
  //myPlayer.play();
	
 });
	
})(jQuery);

I need help here. I am creating a system where the user will be able to update the product stock by uploading the stock of the products according to the id that has been assigned to the product. 
this is how my products table in  looks like in mysql database

I tried the code below but all i could not update my data into my database. And there's not error shown on my code. I do not know what is wrong with my codes. Please help me.
below the code that i use for uploading the CSV file to the data of my product_stock. 

<?php 
include 'conn.php';
if(isset($_POST["add_stock"]))
{
 if($_FILES['product_file']['tmp_name'])
 {
  $filename = explode(".", $_FILES['product_file']['tmp_name']);
  if(end($filename) == "csv")
  {
   $handle = fopen($_FILES['product_file']['tmp_name'], "r");
   while($data = fgetcsv($handle))
   {
    $product_id = mysqli_real_escape_string($conn, $data[0]);
    $product_stock = mysqli_real_escape_string($conn, $data[1]);  
    $product_status = 1 ;
    $query = "UPDATE products SET `product_stock` = '$product_stock', `product_status` = '$product_status' WHERE id = '$product_id'";
    mysqli_query($conn, $query);
   }
   fclose($handle);
   header("location: upload-product.php?updation=1");
  }
  else
  {
   echo '<script>alert("An error occur while uploading product. Please try again.")
   window.location.href = "upload-product.php"</script>';
  }
 }
 else
 {
  echo '<script>alert("No file selected! ")
  window.location.href = "upload-product.php"</script>';
 }
}
if(isset($_GET["updation"]))
{
  echo '<script>alert("Product Stock Updated successfully!")</script>';
}
?>

 <div class="col-12">
            <div class="card card-user">
              <div class="card-header">
                <h5 class="card-title">Update Product Stock</h5>
                <div class="card-body">
                <div class="form-group">
				<label for="file">Update Products stock File (.csv file)</label>
                <a href="assets/templates/product-template.xlsx" title="Download Sample File (Fill In Information and Export As CSV File)" class="mx-2">
				<span class="iconify" data-icon="fa-solid:download" data-inline="false">
				</a>
                </div>
                <form class = "form" action="" method="post" name="uploadCsv" enctype="multipart/form-data">
                <div>
                <input type="file" name="product_file" accept=".csv">
                <div class="row">
                <div class="update ml-auto mr-auto">
                <button type="submit" class="btn btn-primary btn-round" name="add_stock"> Import .cvs file</button>
                </div>
                </div>
                </div>
                </div>
                </form>
                </div>
              </div>

This is the template that i require user to key in and saved it in CSV format before uploading it. 

$sql="SELECT * FROM thetable";
	  
$result = mysqli_query($con,$sql);
  
 echo " <ul>";
	
  while($row = mysqli_fetch_array($result) {
  echo "<li'>";

  echo "<a href='page2.php?id=$row[id]'><img src=$row[image]></a>";
	                                          
  echo "</li>";
    
 }
  
  echo "</ul>";  
           
 ?> 
     
     

<?php
// End while loop.


mysqli_close($con);

?>

$id = $_GET['id']; 

$sql="SELECT id, title, details, image, FROM thetable";
	  
$result = mysqli_query($con,$sql);


$row = mysqli_fetch_array($result);
?>


   <?php echo $row['title'] ?> 
   <?php echo $row['details'] ?>
   <img class='projectItem-pic' src="<?php echo $row['image']?>">

$sql="SELECT * FROM thetable WHERE id = $id";  

<script type="text/javascript">
google.load('visualization', '1', {'packages':['corechart']});
google.setOnLoadCallback(drawChart);


function drawChart() {
var jsonData = $.ajax({
url: "test1.php",
dataType:"json",
async: false,
}).responseText;


var data = new google.visualization.DataTable(jsonData);


var chart = new google.visualization.LineChart(document.getElementById('chart_div'));
chart.draw(data); 
}
</script>