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' => '850', 'nb_visits' => '770', 'nb_actions' => '2,149', 'revenue' => '0', 'nb_visits_lastdate' => 889.0, )'. Try to call this method with the parameters '&format=original&serialize=1'; you will get the original php data structure serialized.