Error: Data structure returned is not convertible in the requested format: Only integer keys supported for array columns on base level. Unsupported string 'totals' found for row 'array ( 'nb_pageviews' => '26,990', 'nb_visits' => '10,777', 'nb_actions' => '31,763', 'revenue' => '91,328.15', 'nb_visits_lastdate' => 8837.0, )'. Try to call this method with the parameters '&format=original&serialize=1'; you will get the original php data structure serialized.