jqGrid. Error to make the sum of a column "Cannot use object of type stdClass"

I'm trying the following example of jqGrid:

http://www.trirand.net/demophp.aspx

   Functionality Misc

   Footer Customization

and get the error detailed below:

Fatal error: Cannot use object of type stdClass as array in C:\htdocs\proyect\js\jquery\jqGrid\php\jqGrid.php(1) : eval()'d code on line 1

The error occurs when you want to sum the column "Freight.":

PHP:

$summaryrows = array("Freight"=>开发者_Go百科array("Freight"=>"SUM"));

The jqGrid version we are using is "3.8.2.1" and PHP "5.3.1".

What is the problem?

Here you can see the bug and the solution: http://www.trirand.net/forum/default.aspx?g=posts&m=4070&#post4070