PHP setcookie返回null

Question

I am working on localhost. I have already a cookie is created with two keys. i want to store the third key, but i couldn't save this third key inside the cookie. It always return null. Also this new key is not available after page refresh. Here is my code

$cart_data = array ('1','2');
$test = setcookie('user_cart', serialize($cart_data), time() + (60 * 20),'/',false,false,false);
var_dump($test);
die;

// Checking output like this. (This code is in other file)

if(isset($_COOKIE['user_cart'])){
echo '<pre>';
print_r($_COOKIE);
die;
}

Answer 1

It was my bad!. First of all you have to serialize the array if you want to store the array in cookie. Secondly, check if the size of cookie (name + value + expiration time) doesn't exceeds the 4KB. This way you can check the size of cookie :

$cookie_length =  strlen(serialize($cart_data));

Suggestion : Don't add huge data in cookie. because whenever it exceeds the limit, it overwrite the previous data stored.