Implode multidimensional array to mysql

Question

this is a code of a shopping cart i'm trying to make. the cart displays the products with: name, size, price, quantity and total. When checked out it saves on Mysql DB.

it saves like this:

user_1 | pants   | XL | 10 $ | 1 | 10 $ | 
user_1 | t-shirt | L  | 5  $ | 2 | 10 $ |
user_2 | socks   | 8  | 7 $  | 5 | 35 $ |

it's creating new row for each product for the same user. But what i need is this:

user_1 | pants, t-shirt   | XL, L | 10, 5 $ | 1, 2 | 20 $ | 
user_2 |      socks       |    8  |    7  $ |    5 | 35 $ |
user_3 | t-shirt, hat     | M, S  | 5, 10 $ | 1, 1 | 15 $ |

for the same user he implodes the data in the column of the same row.

code:

   $products_array[$i] = array("user" => $user, "product" => $name_product, 
   "size" => $size, "price" => $price, "quantity" => $each_item['quantity'], 
   "total" => $cartTotal);


   if (isset($_SESSION["cart_array"]) && count($products_array) > 0 && isset($_POST['addOrder'])) {

foreach ($products_array as $product) {
$user = $_SESSION["user"];
$name_product = $product['name_product'];
$size = $product['size'];
$price = $product['price'];
$quantity = $product['quantity'];
$cartTotal = $product['total'];

$result = mysqli_query($dbc,"INSERT INTO shop (user, product, size, price, quantity, total, date) 
                            VALUES('$user','$name_product','$size','$price','$quantity','$cartTotal',now())");
          header("location: shop_cart.php");
            }
        }

So i been googling arround, and found that what i need is a implode function. But my problem is where and how to set it right. I have tried some code already but it doesnt work.

Appreciate your help. Thank you.