检查多维数组中是否存在值，并在同一个键内编辑其他值

I am trying to check if a value exists in an array and don't add an entire new entry to it, but instead only add to the quantity in the existing data.

My array looks like this:

Array
(
    [0] => Array
        (
            [product] => Douche 1
            [price] => 1200
            [picture] => cms/images/douche.jpg
            [quantity] => 20
        )

    [1] => Array
        (
            [product] => Douche 1
            [price] => 1200
            [picture] => cms/images/douche.jpg
            [quantity] =>  => 18
        )
)

So to check if a value exists I did the following:

if(in_array('Douche 1', array_column($_SESSION['cart'], 'product'))) { // search value in the array
    echo "FOUND";
}

But instead of echoeing FOUND, I need the array to merge in a way, all stays the same, only the quantity needs to add up.

So when my array is like this:

Array
(
    [0] => Array
        (
            [product] => Douche 1
            [price] => 1200
            [picture] => cms/images/douche.jpg
            [quantity] => 20
        )

)

And I add a product with 15 quantity, I want the array to change to this:

Array
(
    [0] => Array
        (
            [product] => Douche 1
            [price] => 1200
            [picture] => cms/images/douche.jpg
            [quantity] => 35
        )

)

So the quantity adds up only when a productname is added that already exists, if it doesn't exist, there just needs to be a new key (with an array in it).

How can I do that?

My entire array code (excluding ajax and my loop) at the moment is this:

if(isset($_POST['product'])){
  $thisProduct = array(
    'product' => $_POST['product'],
    'price' => $_POST['price'],
    'picture' => $_POST['picture'],
    'quantity' => $_POST['quantity'],
  );
  if (isset($_SESSION['cart'])) {
    $_SESSION['cart'][] = $thisProduct;
  } else {
    //Session is not set, setting session now
    $_SESSION['cart'] = array();
    $_SESSION['cart'][] = $thisProduct;
  }
}

if(in_array('Douche 1', array_column($_SESSION['cart'], 'product'))) { // search value in the array
    echo "FOUND";
}

Instead of trying to change after updating your cart array, you maybe could index your array using the name of the product to check if it exists or not :

$prod = $thisProduct['product'] ; // shortcut for name

if (!isset($_SESSION['cart'])) {
   $_SESSION['cart'] = [] ;
}

if (!isset($_SESSION['cart'][$prod])) { // no exists in cart, add it
   $_SESSION['cart'][$prod] = $thisProduct;
}
else { // exists increment quantity
   $_SESSION['cart'][$prod]['quantity'] += $thisProduct['quantity'];
}