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' =&gt; '25,540',
  'nb_visits' =&gt; '10,490',
  'hits' =&gt; '31,009',
  'nb_actions' =&gt; '30,391',
  'revenue' =&gt; '73,853',
  'previous_nb_pageviews' =&gt; '27,882',
  'previous_nb_visits' =&gt; '10,958',
  'previous_hits' =&gt; '33,396',
  'previous_nb_actions' =&gt; '32,791',
  'previous_revenue' =&gt; '95,197.05',
)'. Try to call this method with the parameters '&amp;format=original&amp;serialize=1'; you will get the original php data structure serialized.