Can´t show message after form submit with header("location:") - php

Question

I've search the forum for the same situation that I have but still couldn't find the solution. It's probably a piece of cake but I can't figure it out why my $_GET[] doesn't work.
I've created a product page and when I add something to the cart I want to display a message. I've made it work with the url in the form action but then my cart counter in the header stops working properly.
If it's possible I don't want to add any extra in the url like a "?success" because then it just keeps adding ?success to the url if I add more to the cart, that works in action but not with header() ?
Here is my code for the product page:
<?php include_once '../header.php';
$message = "";
$product = New Product;
$cart_data = [];
// if the variables are set - run the following statement
if(isset($_POST["addtocart"])) {
if(isset($_COOKIE["cart"])) {
// Removes backlashes and dont replace previous item, gives every item a new row.
$cookie_data = stripslashes($_COOKIE['cart']);
$cart_data = json_decode($cookie_data, true);
}
// Returns the productid and Size in the array
$item_list = array_column($cart_data, 'ProductsId');
$size_list = array_column($cart_data, 'Size');
// Returns the value if the statement is true
if(in_array($_POST["ProductsId"], $item_list) && in_array($_POST['selectedSize'], $size_list)) {
// A foreachloop that repeats the array value of the selected key variable.
foreach($cart_data as $keys => $values) {
if($cart_data[$keys]["ProductsId"] == $_POST["ProductsId"] && $cart_data[$keys]["Size"] == $_POST["selectedSize"]) {
$cart_data[$keys]["quantity"] = $cart_data[$keys]["quantity"] + $_POST["quantity"];
}
}
}
else {
$item_array = array(
'Img' => $Img = filter_var($_POST["Img"], FILTER_SANITIZE_STRING),
'ProductName' => $ProductName = filter_var($_POST["ProductName"], FILTER_SANITIZE_STRING),
'Size' => $Size = filter_var($_POST['selectedSize'], FILTER_SANITIZE_STRING),
'ProductsId' => $ProductsId = filter_var($_POST["ProductsId"], FILTER_SANITIZE_NUMBER_INT),
'Price' => $Price = filter_var($_POST["Price"], FILTER_SANITIZE_NUMBER_INT),
'quantity' => $quantity = filter_var($_POST["quantity"], FILTER_SANITIZE_NUMBER_INT),
);
$cart_data[] = $item_array;
}
$item_data = json_encode($cart_data);
setcookie('cart', $item_data, time() +(3600),'/');
header("location: product-detail.php?product=".$_GET['product']."?success");
}
if(isset($_GET['success'])) {
$message = "Varan lades till i varukorgen";
};
var_dump($message);
?>
<main id="product-content">
<section>
<form method="post" name="cartCount" action="">
<!-- product-detail.php?product=<?php echo $_GET['product']; ?> -->
<?php if(isset($_GET['product'])) {
$product->ProductsId = $_GET['product'];
$product->ProductId = $_GET['product'];
$product->ProductsId = $_GET['product'];
} else {
$product->ProductsId = $_POST['ProductsId'];
}
$result = $product->get_product();
$test = $product->get_productvariation();
while ($row = $result->fetch()) { ?>
<div class="product-card-detail">
<div class="product-image-wrapper">
<img class="product-image" src="../<?php echo $row['Img'];?>" >
<input type ="hidden" name="Img" value="<?php echo $row['Img'] ?>">
<?php $results = $product->get_images();
$Images = $results->fetch();
if(isset($Images['Image'])) { ?>
<img class="product-image" src="../<?php echo $Images['Image'];?>">
<?php } ?>
</div>
<div class="product-details-text">
<h2 class="title"><?php echo $row['ProductName']; ?></h2>
<input type ="hidden" name="ProductName" value="<?php echo $row['ProductName'] ?>">
<span class="price"><?php echo $row['Price'];?> SEK</span>
<input type ="hidden" name="Price" value="<?php echo $row['Price'] ?>">
<span class="select-title">Storlek</span>
<select class="size" name="selectedSize">
<?php while ($sizeRow = $test->fetch()) { ?>
<option>
<?php echo $sizeRow['Size']; ?>
</option>
<?php } ?>
</select>
<input type="hidden" name="quantity" value="1" />
<input type="submit" class="addtocart-btn" name="addtocart" value="Lägg i varukorgen"/>
<div><?php echo $message ?></div>
<input type ="hidden" name="ProductsId" value="<?php echo $row['ProductsId'] ?>">
<span class="title-description">Beskrivning</span>
<p class="description"><?php echo $row['Description']; ?></p>
</div>
</div>
<?php } ?>
</form>
</section>
</main>
<?php include_once "../footer.php";?>
I've made a test page that works exactly as expected so I can only think that is has to be something about the url?
Test code:
<?php
$message ="";
if(isset($_POST['submit'])) {
header("location: index.php?success");
}
if(isset($_GET['success'])) {
$message = "hello";
}
var_dump($message);
?>
<form method="post" action="">
<input text name="name" value="">
<input type="submit" name="submit" value="submit">
<?php echo $message ?>
</form>
Glad if anyone can see why it doesn't work!

Answer 1

You have made a mistake:
header("location: product-detail.php?product=".$_GET['product']."?success");
See the above line and notice that you are appending param success with ?.
Make it & as:
header("location: product-detail.php?product=".$_GET['product']."&success");