在图表上显示google analytics api查询

I am using Google Analytics Api V3 and trying to show query results on the chart. I have this code at the moment but it's not showing on the chart. I think I am not passing the rows to chart correctly because I messed up foreach loop

  google.load('visualization', '1.0', {'packages':['corechart']});

  google.setOnLoadCallback(drawChart);

  function drawChart() {

    var data = new google.visualization.DataTable();
    data.addColumn('string', 'Topping');
    data.addColumn('number', 'Slices');
    data.addRows([
      <?php

        $first_date = '30daysAgo';
        $last_date = 'yesterday';
        $metrics = 'ga:sessions';
        $optParams = array(
          'dimensions' => 'ga:browser',
          'sort' => '-ga:sessions',
          'max-results' => '10'
        );

        try {

            $results = $analytics->data_ga->get($analytics_id, $first_date, $last_date, $metrics, $optParams);

            function printDataTable($results) {
                if (count($results->getRows()) > 0) {
                  $value .= '';

                  foreach ($results->getRows() as $row) {
                    $value .= '';
                      foreach ($row as $cell) {
                        $value .= ''
                               . htmlspecialchars($cell, ENT_NOQUOTES)
                               . ' ';
                  }
                }

                } else {
                  $value .= 'No results found';
              }

              print $value;
            }

          print_r(printDataTable($results));

        }
         catch(Exception $e) {
            printf('There was an Error in your query: %s', $e->getMessage());
        }
      ?>
    ]);

    var options = {'title':'Title',
                   'width':400,
                   'height':300};

    var chart = new google.visualization.PieChart(document.getElementById('chart_div'));
    chart.draw(data, options);
  }