Error: Data structure returned is not convertible in the requested format: Only integer keys supported for array columns on base level. Unsupported string 'metadata' found for row 'array (
  'metrics' =&gt; 
  array (
    'nb_visits' =&gt; 
    array (
      'name' =&gt; 'Visits',
      'min' =&gt; 0,
      'max' =&gt; 2.0,
    ),
    'nb_uniq_visitors' =&gt; 
    array (
      'name' =&gt; 'Unique visitors',
      'min' =&gt; 0,
      'max' =&gt; 2.0,
    ),
    'nb_actions' =&gt; 
    array (
      'name' =&gt; 'Actions',
      'min' =&gt; 0,
      'max' =&gt; 3.0,
    ),
    'nb_actions_per_visit' =&gt; 
    array (
      'name' =&gt; 'Actions per Visit',
      'min' =&gt; 0,
      'max' =&gt; 2.0,
    ),
    'avg_time_'. Try to call this method with the parameters '&amp;format=original&amp;serialize=1'; you will get the original php data structure serialized.