How to fix "Fatal error: Uncaught Error: Unsupported operand types" when multiply two values

Question

When click on update button, it does'n update both quantity and his price only updated quantity.It shows fatal error: Uncaught Error: Unsupported operand types on line where multiply the quantity and price_value. Thank u

<form action="" method="POST" enctype="multipart/form-data">    
<input type="hidden" name="product_id[]" value="<?php echo $product_id; ?>">
<input type="hidden" name="size_id[]" value="<?php echo $size_id_2; ?>">
<input name="quantity[]" value="<?php echo $quantity; ?>" type="number" id="number" >
<input type="hidden" name="price[]" value="<?php echo $price; ?>">
<?php

    if (isset($_POST['update'])) {

      $product_id = $_POST['product_id'];
      $size_id = $_POST['size_id'];
      $quantity = $_POST['quantity'];
      $price_value = $_POST['price'];

      $updated_price = $price_value * $quantity;

      foreach($product_id as $index => $h){
      $v = $size_id[$index];
      $q = $quantity[$index];
      $p = $updated_price[$index];
      $update_query = "UPDATE cart SET product_price='$p',quantity='$q' WHERE product_id='$h' AND size_id='$v'";
      $run_query = mysqli_query($con , $update_query);

      if($run_query){
        echo"<script>window.open('cart.php','_self')</script>";
            }
          }
        }

    ?>      
<button type="submit" name="update" class="btn btn-icon btn-icon-left btn-primary btn-shape-circle offset-top-35"><i class="fa fa-wrench"></i> Update Cart</button>
</form>

Answer 1

<form action="" method="POST" enctype="multipart/form-data">    
<input type="hidden" name="product_id[]" value="<?php echo $product_id; ?>">
<input type="hidden" name="size_id[]" value="<?php echo $size_id_2; ?>">
<input name="quantity[]" value="<?php echo $quantity; ?>" type="number" id="number" >
<input type="hidden" name="price[]" value="<?php echo $price; ?>">
<?php

if (isset($_POST['update'])) {

  $product_id = $_POST['product_id'];
  $size_id = $_POST['size_id'];
  $quantity = $_POST['quantity'];
  $price_value = $_POST['price'];

      $total_price = array($price_value);

      $values_multiple = array_sum($total_price);

      foreach($product_id as $index => $h){

      $v = $size_id[$index];
      $q = $quantity[$index];
      $p  = $price_value[$index]; 

      $values_multiple = $q * $p;

      $total_grand = $values_multiple;

    $update_query = "UPDATE cart SET product_price='$total_grand',quantity='$q' WHERE product_id='$h' AND size_id='$v'";
      $run_query = mysqli_query($con , $update_query);

      if($run_query){
        echo"<script>window.open('cart.php','_self')</script>";
            }

          }
        }

    ?>