View difference between Paste ID: tRbJKt37 and BRU1BP2E

 /**
- * Restricts which products can be added to the cart at the same time. Tested
+ * Restricts which products can be added to the cart at the same time.
- * with WooCommerce up to version 2.5.
+ * Version for WooCommerce 3.x and later.
- *
+
  * HOW TO USE THIS CODE
  * 1. Add the code to the bottom of your theme's functions.php file (see https://www.skyverge.com/blog/add-custom-code-to-wordpress/).
  * 2. Set the IDs of the products that are allowed to be added to the cart at the same time.
  * 3. Amend the message displayed to customers when products are unavailable after the specified
  *    products have been added to the cart (see function woocommerce_get_price_html(), below).
  *
  * GPL DISCLAIMER
  * Because this code program is free of charge, there is no warranty for it, to the extent permitted by applicable law.
  * Except when otherwise stated in writing the copyright holders and/or other parties provide the program "as is"
  * without warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of
  * merchantability and fitness for a particular purpose. The entire risk as to the quality and performance of the program
  * is with you. should the program prove defective, you assume the cost of all necessary servicing, repair or correction.
  *
  * Need a consultation, or assistance to customise this code? Find us on Codeable: https://aelia.co/hire_us
  */
 
 /**
  * Retrieves the cart contents. We can't just call WC_Cart::get_cart(), because
  * such method runs multiple actions and filters, which we don't want to trigger
  * at this stage.
  *
  * @author Aelia <support@aelia.co>
  */
 function aelia_get_cart_contents() {
   $cart_contents = array();
   /**
    * Load the cart object. This defaults to the persistant cart if null.
    */
   $cart = WC()->session->get( 'cart', null );
 
-  if ( is_null( $cart ) && ( $saved_cart = get_user_meta( get_current_user_id(), '_woocommerce_persistent_cart', true ) ) ) {
+	if ( is_null( $cart ) && ( $saved_cart = get_user_meta( get_current_user_id(), '_woocommerce_persistent_cart_' . get_current_blog_id(), true ) ) ) { // @codingStandardsIgnoreLine
-    $cart = $saved_cart['cart'];
+		$cart                = $saved_cart['cart'];
-  } elseif ( is_null( $cart ) ) {
+	}
-    $cart = array();
+	elseif ( is_null( $cart ) ) {
 		$cart = array();
 	}
 	elseif ( is_array( $cart ) && ( $saved_cart = get_user_meta( get_current_user_id(), '_woocommerce_persistent_cart_' . get_current_blog_id(), true ) ) ) { // @codingStandardsIgnoreLine
 		$cart                = array_merge( $saved_cart['cart'], $cart );
 	}
 
   if ( is_array( $cart ) ) {
     foreach ( $cart as $key => $values ) {
       $_product = wc_get_product( $values['variation_id'] ? $values['variation_id'] : $values['product_id'] );
 
       if ( ! empty( $_product ) && $_product->exists() && $values['quantity'] > 0 ) {
         if ( $_product->is_purchasable() ) {
           // Put session data into array. Run through filter so other plugins can load their own session data
           $session_data = array_merge( $values, array( 'data' => $_product ) );
           $cart_contents[ $key ] = apply_filters( 'woocommerce_get_cart_item_from_session', $session_data, $values, $key );
         }
       }
     }
   }
   return $cart_contents;
 }
 
 // Step 1 - Keep track of cart contents
 add_action('wp_loaded', function() {
   // If there is no session, then we don't have a cart and we should not take
   // any action
   if(!is_object(WC()->session)) {
     return;
   }
 
   // This variable must be global, we will need it later. If this code were
   // packaged as a plugin, a property could be used instead
   global $allowed_cart_items;
-    737,
+
-    832,
+
   global $restricted_cart_items;
   $restricted_cart_items = array(
 		// Set the IDs of the products that can be added to the cart at the same time
     1,
-    if(in_array($item['data']->id, $restricted_cart_items)) {
+    2,
-      $allowed_cart_items[] = $item['data']->id;
+    3,
   );
 
   // "Snoop" into the cart contents, without actually loading the whole cart
   foreach(aelia_get_cart_contents() as $item) {
     if(in_array($item['data']->get_id(), $restricted_cart_items)) {
       $allowed_cart_items[] = $item['data']->get_id();
 
       // If you need to allow MULTIPLE restricted items in the cart, comment
       // the line below
       break;
     }
-
+
 
   // Step 2 - Make disallowed products "not purchasable"
   add_filter('woocommerce_is_purchasable', function($is_purchasable, $product) {
     global $restricted_cart_items;
     global $allowed_cart_items;
-
+
     // If any of the restricted products is in the cart, any other must be made
-      $is_purchasable = in_array($product->id, $allowed_cart_items);
+
     if(!empty($allowed_cart_items)) {
       // To allow MULTIPLE products from the restricted ones, use the line below
       //$is_purchasable = in_array($product->id, $allowed_cart_items) || in_array($product->id, $restricted_cart_items);
 
       // To allow a SINGLE  products from the restricted ones, use the line below
       $is_purchasable = in_array($product->get_id(), $allowed_cart_items);
     }
     return $is_purchasable;
   }, 10, 2);
 }, 10);
 
 // Step 3 - Explain customers why they can't add some products to the cart
 add_filter('woocommerce_get_price_html', function($price_html, $product) {
   if(!$product->is_purchasable() && is_product()) {
     $price_html .= '<p>' . __('This product cannot be purchased together with "Product X" or "Product Y". If you wish to buy this product, please remove the other products from the cart.', 'woocommerce') . '</p>';
   }
   return $price_html;
 }, 10, 2);