<?php
  // ********************************
  // get product data from upload xml
  // ********************************
  // ...
  $xml_webgroup_id = array();
  $xml = simplexml_load_file("./path/to/uploaded/products.xml");     // FROM XML
  foreach ( $xml as $prd ) {
     $xml_title = $prd->name . "\n";
     $xml_code = $prd->code . "\n";
     $xml_id = $prd->id . "\n";
     foreach ( $prd->ProductWebGroups->ProductWebGroup as $wg ) {
        $xml_webgroup_id[] = $wg;
        }
 
     if ( $product_q = commerce_product_load_by_sku( $xml_id ) ) {
           echo "\nUpdate...\n";
           $product = new StdClass();
           $product->product_id = $product_q->product_id; // here is set id for the modify product
           $product->title = $xml_title;
           $product->sku = $xml_id;
           $product->status = '1';
           $product->revision_timestamp = time();
           // $product->type = $xml_producttype;
           $product->type = 'product';
           $product->uid = $user->uid;
           $product->created = time();
           $product->changed = time();
           $product->field_symbol_code[LANGUAGE_NONE][0]['value'] = $xml_code;
           $i = 0;
           foreach ( $xml_webgroup_id as $wid ) {
              $product->field_productgroups[LANGUAGE_NONE][$i]['tid'] = $xml_webgroup_id[$i];
              $i++;
              } // foreach
           commerce_product_save($product);
           $xml_webgroup_id = array(); // empty variable
 
        } else {
           echo "\nInsert...\n";
           $product = commerce_product_new('product');
           $product->title = $xml_title;
           $product->sku = $xml_id;
           $product->status = '1';
           $product->revision_timestamp = time();
           // $product->type = $xml_producttype;
           $product->uid = $user->uid;
           $product->created = time();
           $product->changed = time();
           $product->field_symbol_code[LANGUAGE_NONE][0]['value'] = $xml_code;
           $i = 0;
           foreach ( $xml_webgroup_id as $wid ) {
              $product->field_productgroups[LANGUAGE_NONE][$i]['tid'] = $xml_webgroup_id[$i];
              $i++;
              } // foreach
           commerce_product_save($product);
           $xml_webgroup_id = array(); // empty variable
        } // if
 
  } // end of foreach
 
  // ...
?>