Problème d'insertion en db de fichiers renommés

$old_file_names =  !empty($row['product_images']) ? $row['product_images'] : null; 								   
var_dump($old_file_names);
$exploded = !empty($old_file_names) && is_string($old_file_names) ? explode("," , $old_file_names) : array();	
var_dump($exploded );

$old_file_names =  !empty($row['product_images']) ? $row['product_images'] : null; 								   
var_dump($old_file_names);
$exploded = !empty($old_file_names) && is_string($old_file_names) ? explode("," , $old_file_names) : array();	
var_dump($exploded );

 $fileCount = count($_FILES["product_images"]['name']);
 for ( $i=0; $i < $fileCount; $i++ )
 {
   $path = "product_images/";
   $name = strtolower($_FILES['product_images']['name'][$i]);  
 }   
 
    $product_images ="";
    $valid_formats = array("jpg", "png", "jpeg", "webp");
    $max_file_size = 358400; 
    $path = "product_images/"; // Upload directory
    $count = 0;

     foreach ($_FILES['product_images']['name'] as $f => $name) 
 {     
        if ($_FILES['product_images']['error'][$f] == 4) 
  {
            continue; 
        }          
        if ($_FILES['product_images']['error'][$f] == 0) 
  {              
            if ($_FILES['product_images']['size'][$f] > $max_file_size) 
   {
                $message[] = "$name is too large!.";
                continue; 
            }
            elseif( ! in_array(pathinfo($name, PATHINFO_EXTENSION), $valid_formats) )
   {
                $message[] = "$name is not a valid format";
                continue;  
            }
            else{        
     
                if(move_uploaded_file($_FILES["product_images"]["tmp_name"][$f], $path.$name))
    
               $product_images .= $path.$name.', ';
    //  var_dump($product_images);
      $count++; // Number of successfully uploaded file      
            }
        }

<?php

//Initialisation/déclaration des variables/constantes :
$valid_formats = array("jpg", "png", "jpeg", "webp");
$max_file_size = 358400;
$path = "product_images/"; // Upload directory
$arrFilesNames = array();
$message = array();

$phpFileUploadErrors = array(
    0 => 'There is no error, the file uploaded with success',
    1 => 'The uploaded file exceeds the upload_max_filesize directive in php.ini',
    2 => 'The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form',
    3 => 'The uploaded file was only partially uploaded',
    4 => 'No file was uploaded',
    6 => 'Missing a temporary folder',
    7 => 'Failed to write file to disk.',
    8 => 'A PHP extension stopped the file upload.',
);

//récupération propre des variables AVANT de les utiliser :
$file_product_images = !empty($_FILES["product_images"]) ? $_FILES["product_images"] : NULL;
$file_product_images_names = !empty($file_product_images['name']) ? $file_product_images['name'] : NULL;

//On boucle sur les fichiers
if(!empty($file_product_images_names)){
  foreach ($file_product_images_names as $f => $name) {
    $fileError = $file_product_images['error'][$f];
    if(!$fileError){
      $fileSize = $file_product_images['size'][$f];
      if($fileSize > $max_file_size){
        $message[] = "$name is too large!.";
      } else{
        if(!in_array(pathinfo($name, PATHINFO_EXTENSION), $valid_formats) ) {
          $message[] = "$name is not a valid format";
        }else{
          $tmp_name = $file_product_images["tmp_name"][$f];
          if( move_uploaded_file($tmp_name, $path . strtolower($name))) {
            $arrFilesNames[] = $name; // ou $path.$name  si tu veux absolument stocker le path avec le nom de ton image
          } else {
            $message[] = "$name : Upload error";
          }       
        }
      }
    } else {
      $message[] = !empty($phpFileUploadErrors[$fileError]) ? $phpFileUploadErrors[$fileError] : " Unknown error !";
    }
  }

  // on reconstruit ta chaine en faisant un join sur l'array
  $product_images = !empty($arrFilesNames) ? join(',',$arrFilesNames) : "";
}

<?php
//Affichage des erreurs PHP ( A PLACER AU DEBUT DE TON SCRIPT.... )
error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);

date_default_timezone_set("Europe/Paris");


// Include de ton fichier de connexion à la bdd :
// ... ??? 
// require_once 'ton_fichier_de_connexion_a_ta_bdd.php'


// FONCTIONS
function getPOST($varName,$default = NULL ){
  return !empty($_POST[$varName]) ? $_POST[$varName] : $default;
}

function insertBdd(){
	global $con;
	
	// Récupérationb PROPRE DES VARIABLES AVANT DE LES UTILISER
	$product_title = getPOST('product_title'); 
	$customer_profile_id = getPOST('customer_profile_id');
	$product_cat = getPOST('product_cat');
	$product_subcat = getPOST('product_subcat');
	$product_length = getPOST('product_length');
	$product_main_color = getPOST('product_main_color');
	$product_pattern = getPOST('product_pattern');
	$product_brand = getPOST('product_brand');
	$product_price = getPOST('product_price');
	$product_keywords = getPOST('product_keywords');
	$product_description = getPOST('product_description');
	$purchased_stock_34 = getPOST('purchased_stock_34');
	$purchased_stock_36 = getPOST('purchased_stock_36');
	$purchased_stock_38 = getPOST('purchased_stock_38');
	$purchased_stock_40 = getPOST('purchased_stock_40');
	$purchased_stock_42 = getPOST('purchased_stock_42');
	$purchased_stock_44 = getPOST('purchased_stock_44');
	$product_variation_colors =  implode(",", getPOST('product_variation_colors'));
	$product_attributes =  implode(",", getPOST('product_attributes')); 
	$product_occasions =  implode(",", getPOST('product_occasions')); 
	$product_materials =  implode(",", getPOST('product_materials')); 
	
	$date = date('Y-m-d h:i:s');	
	$created_by =  !empty($_SESSION['admin_name']) ? $_SESSION['admin_name']: NULL;

	$product_images = uploadFiles();

 
    $stmt = $con->prepare("INSERT  into products ( 
		product_title, 
		customer_profile_id, 
		p_cat_id, 
		product_subcat_id,  
		product_length, 
		product_main_color, 
		product_pattern, 
		product_attributes,
		product_occasions,
		product_material,
		product_brand,
		product_price, 
		product_keywords, 
		product_description, 
		product_images, 
		product_variation_colors, 
		purchased_stock_34, 
		purchased_stock_36, 
		purchased_stock_38, 
		purchased_stock_40, 
		purchased_stock_42, 
		purchased_stock_44,  
		created_by, 
		created_on, 
		last_modified_by, 
		last_modified_on  ) 
		VALUES (?, ?, ?, ?,?, ?,?, ?,?, ?,?, ?,?, ?,?, ?,?, ?,?, ?,?, ?, ?, ?, ?, ?)");
		
	$stmt->bind_param("siiisiiiiiidssssiiiiiissss", 
		 $product_title, 
		 $customer_profile_id, 
		 $product_cat, 
		 $product_subcat, 
		 $product_length, 
		 $product_main_color, 
		 $product_pattern,
		 $product_attributes,
		 $product_occasions,
		 $product_materials,
		 $product_brand, 
		 $product_price, 
		 $product_keywords, 
		 $product_description,
		 "", //$product_images
		 $product_variation_colors, 
		 $purchased_stock_34, 
		 $purchased_stock_36, 
		 $purchased_stock_38, 
		 $purchased_stock_40, 
		 $purchased_stock_42, 
		 $purchased_stock_44, 
		 $created_by, 
		 $date, 
		 $created_by, 
		 $date
    );

	if(!$stmt->execute()) {
		trigger_error("there was an error....".$con->error, E_USER_WARNING); 
		$stmt->close();
		return false;
    }
	
	$product_id = mysqli_stmt_insert_id($stmt);   

	return $product_id;
}

function uploadFiles($product_id){
	//Initialisation/déclaration des variables/constantes :

	$valid_formats = array("jpg", "png", "jpeg", "webp");
	$max_file_size = 358400;
	$path = "product_images/"; // Upload directory
	$arrFilesNames = array();
	$message = array();

	$phpFileUploadErrors = array(
		0 => 'There is no error, the file uploaded with success',
		1 => 'The uploaded file exceeds the upload_max_filesize directive in php.ini',
		2 => 'The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form',
		3 => 'The uploaded file was only partially uploaded',
		4 => 'No file was uploaded',
		6 => 'Missing a temporary folder',
		7 => 'Failed to write file to disk.',
		8 => 'A PHP extension stopped the file upload.',
	);

	//récupération propre des variables AVANT de les utiliser :
	$file_product_images = !empty($_FILES["product_images"]) ? $_FILES["product_images"] : NULL;
	$file_product_images_names = !empty($file_product_images['name']) ? $file_product_images['name'] : NULL;

	//On boucle sur les fichiers
	if(!empty($file_product_images_names)){
	  foreach ($file_product_images_names as $f => $name) {
		$fileError = $file_product_images['error'][$f];
		if(!$fileError){
		  $fileSize = $file_product_images['size'][$f];
		  if($fileSize > $max_file_size){
			$message[] = "$name is too large!.";
		  } else{
			if(!in_array(pathinfo($name, PATHINFO_EXTENSION), $valid_formats) ) {
			  $message[] = "$name is not a valid format";
			}else{
			  $tmp_name = $file_product_images["tmp_name"][$f];
			  $without_extension = pathinfo($name, PATHINFO_FILENAME); 
        $ext = pathinfo($name, PATHINFO_EXTENSION ); 
			  $new_filename = $path.$without_extension.'_ref_'.$product_id.'.'.$ext;
			  if( move_uploaded_file($tmp_name, strtolower($new_filename))) {
           $arrFilesNames[] = $new_filename; 
			  } else {
			    $message[] = "$name : Upload error";
			  }       
			}
		  }
		} else {
		  $message[] = !empty($phpFileUploadErrors[$fileError]) ? $phpFileUploadErrors[$fileError] : " Unknown error !";
		}
	  }
  
	}
  
  if(!empty($message)){
    trigger_error("there was an error...." . print_r($message,true), E_USER_WARNING); 
    return false;
  }
  
	// on reconstruit ta chaine en faisant un join sur l'array
	$product_images = !empty($arrFilesNames) ? join("," , $arrFilesNames) : ""; // join. (PHP 4, PHP 5, PHP 7). join — Alias de implode().
	var_dump($arrFilesNames);
	var_dump($product_images);
	     
	return $product_images;
}

function updateProductImages($product_id,$product_images){
	global $con;
	$stmt = $con->prepare(" update products set product_images=? WHERE product_id=? ");
	$stmt->bind_param('si', $product_images, $product_id);
	if(!$stmt->execute()) {
		trigger_error("there was an error....".$con->error, E_USER_WARNING); 
		$stmt->close();
		return false;
	}
  
  return true;
}

// Traitement du formulaire

if(isset($_POST['submit'])) {
  
	//ETAPE 1 - On créé le produit en BDD
	$product_id = insertBdd();

	//ETAPE 2 - On UPLOAD les images ET on les renomme directement ...
	$product_images =  uploadFiles($product_id)
	
	//ETAPE 3 - On met à jour le champs product_images du produit
  $updImages = updateProductImages($product_id,$product_images)  

  // Si on a bien un product_id et que l'update des images s'est bien fait :    
  if ($product_id && $updImages) { 
    echo "<script>alert('Product has been inserted sucessfully')</script>";}
    echo "<script>window.open('index.php?view_products','_self')</script>";
  }
     
    
}
?>
<!Doctype html>
<html lang='en'>
 <!-- la suite de ton code html .... -->