Prevent duplicate items being added to cart in PHP - php

Question

I'm using a session array to store products in a cart.
If the selected product is already in the cart, instead of the product being added again, I want to display a message informing the user that the product has already been added.
I've tried looping through the array to find the matching key. I've also tried the in_array($var1,$var2) function. With these, the status tells the user their product is already in the cart but adds the product anyway.
The last thing I tried was the array_search function to check if the key exists but the product is still getting added to the cart regardless.
if(isset($_GET['productID']) && $_GET['productID'] != "") {
$product = $_GET['productID'];
$product = (string)$product;
$result_product = GetSpecificProduct($product);
if(!empty($result_product)) {
$cart_array[$result_product['ProductID']] = array(
'ProductID'=>$result_product['ProductID'],
'ProductName'=>$result_product['ProductName'],
'Price'=>$result_product['Price'],
'Specifications'=>$result_product['Specifications'],
'CO'=>$result_product['CO'],
'CatID'=>$result_product['CatID'],
'Name'=>$result_product['Name'],
'Quantity'=>1
);
}
if(empty($_SESSION['tocoto_cart'])){
$_SESSION['tocoto_cart'] = $cart_array;
$status = $result_product['ProductName']." added to your cart.";
}else if(!empty($_SESSION['tocoto_cart'])) {
$key = array_search($result_product['ProductID'],$_SESSION['tocoto_cart']);
if($key !== false) {
$status = "Selected product is already in your cart.";
} else {
$status = $result_product['ProductName'] . " added to your cart.";
$_SESSION['tocoto_cart'] = array_merge($_SESSION['tocoto_cart'],$cart_array );
}

Answer 1

try to do something like this
$array = $_SESSION['tocoto_cart'];
$key = array_search($result_product['ProductID'], array_column($array, 'ProductID'));
if($key !== false) {
$status = "Selected product is already in your cart.";
} else {
$status = $result_product['ProductName'] . " added to your cart.";
$_SESSION['tocoto_cart'] = array_merge( $_SESSION['tocoto_cart'], $cart_array );
}

Answer 2

Bad approach to store cart items in session, because when server (or php-fpm/apache process) restarts, all carts will be cleared with the sessions.
Store cart items in DB, and to be sure that item is unique within the single cart use combined unique constraint on user_token, cart_id and item_id with ON DUPLICATE KEY UPDATE quantity = quantity + 1 SQL
If this is too complex for you, try to modify this piece of your code
$key = array_search($result_product['ProductID'],$_SESSION['tocoto_cart']);
if($key !== false) {
to
if (array_key_exists($result_product['ProductID'],$_SESSION['tocoto_cart'])) {
$_SESSION['tocoto_cart'][$result_product['ProductID']]['Quantity'] += 1;
}