I am getting the following warning when trying to add data to a session (and checking if it already exists).
Warning: in_array() expects parameter 2 to be array, null given
How can I fix this?
The code it is referring to:
if(isset($_GET['product']) && !in_array($_GET['product'], $_SESSION['product'])){
$_SESSION['product'][] = $_GET['product'];
}
I only get this warning when adding the first product on a cleaned browser. When I remove it and add another product the warning is gone. Same if I add a second product.