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<?php

      $product_ids = array();

      $order = commerce_order_load(4);

      foreach (entity_metadata_wrapper('commerce_order', $order)->commerce_line_items as $delta => $line_item_wrapper) {
         if (in_array($line_item_wrapper->type->value(), commerce_product_line_item_types())) {
           //$product_ids[] = $line_item_wrapper->commerce_product->raw();
           $product_ids[] = $line_item_wrapper->commerce_product->raw();
         }
       }


      dpm($product_ids);