title: WC()->cart->get_cart() shows empty but not on cart page
body: <p>I have a PHP script on a WooCommerce webserver that interfaces with an Android app I am developing. I mainly use it for logging into Wordpress accounts and adding/removing products to the WooCommerce cart. </p>
  
  <p>These functions work just fine:</p>
  
  <pre><code>function add_to_cart(){
      return WC()-&gt;cart-&gt;add_to_cart(
          $_POST['product_id'], 
          $_POST['quantity'],
          $_POST['variation_id'],
          null, 
          null);
  }
  
  function remove_from_cart(){
      if(empty($_POST['cart_item_key'])){
          return 'Please specify cart_item_key';
      }
      WC()-&gt;cart-&gt;remove_cart_item($_POST['cart_item_key']);
      return 'Product removed from cart!';
  }
  </code></pre>
  
  <p>This function also works, but it return an empty array...</p>
  
  <pre><code>function get_cart_contents(){
      return WC()-&gt;cart-&gt;get_cart();
  }
  </code></pre>
  
  <p>However I know that the cart is not empty because when I add a product to the cart on the app it shows in the cart on the website. Is there a different function I should be calling? Am I forgetting to call something?</p>
  
  <h2><i>I'm on a learn-implement basis with PHP, constructive criticism welcome</i></h2>