Error: Data structure returned is not convertible in the requested format. Try to call this method with the parameters '&format=original&serialize=1'; you will get the original php data structure serialized. The data structure looks like this: $data = array ( 'Limitation' => array ( 0 => 'Multi dimensional arrays is only supported by format=JSON', 1 => 'Known limitation', ), 'Second Dimension' => array ( 0 => true, 1 => false, 2 => 1, 3 => 0, 4 => 152, 5 => 'test', 6 => array ( 42 => 'end', ), ), );