Error: Data structure returned is not convertible in the requested format: Only integer keys supported for array columns on base level. Unsupported string 'firstVisit' found for row 'array ( 'date' => 1711715148, 'prettyDate' => 'Friday, March 29, 2024', 'daysAgo' => 0, 'referrerType' => false, 'referrerUrl' => '', 'referralSummary' => 'Direct Entry', )'. Try to call this method with the parameters '&format=original&serialize=1'; you will get the original php data structure serialized.