? commerce-987624-2.patch
Index: modules/cart/commerce_cart.module
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/commerce/modules/cart/commerce_cart.module,v
retrieving revision 1.70
diff -u -p -r1.70 commerce_cart.module
--- modules/cart/commerce_cart.module	2 Dec 2010 06:27:37 -0000	1.70
+++ modules/cart/commerce_cart.module	2 Dec 2010 23:11:09 -0000
@@ -501,9 +501,10 @@ function commerce_cart_add_to_cart_form(
     // If the form is for a single product, store the product_id in a hidden
     // form field for use by the submit handler.
     if (count($products) == 1) {
+      $products_keys = array_keys($products);
       $form['product_id'] = array(
         '#type' => 'hidden',
-        '#value' => array_shift(array_keys($products)),
+        '#value' => array_shift($products_keys),
       );
     }
     else {