有没有人用过google chart api 折线图，把php里的数组放到js里显示折线图

<?php
$json =json_encode($myData['CourseInfo']);
?>
<script type="text/javascript" src="https://www.google.com/jsapi"></script>
    <script type="text/javascript">
    google.load("visualization", "1", {packages:["corechart"]});
    google.setOnLoadCallback(drawChart);
    function drawChart() {
     var json = <?php echo $json?>;
     var data = new google.visualization.DataTable();
     data.addColumn('string', 'day');
     data.addColumn('number', '长期数量');
     data.addColumn('number', '非长期数量');
     var cnt = json.length;     var arr=new Array();
     for(i=0;i<cnt;i++){
     var j='\''+json[i]['tdate']+'\'';
     var x = json[i]['coulong'];
     var y = json[i]['coulongun'];
     arr[i] = '[' + j + ',' +x+','+ y+']';
     }
     alert(arr);弹出（['2012-03-27',0,119],['2012-03-26',0,335],['2012-03-25',0,539],['2012-03-24',0,534],['2012-03-23',0,344],['2012-03-22',0,335],['2012-03-21',0,343],['2012-03-20',0,301]）
     date.addRows([arr]);这样折线图不会显示出来
//     data.addRows([
//         ['2012-03-27',0,119],['2012-03-26',0,335],['2012-03-25',0,539],['2012-03-24',0,534],['2012-03-23',0,344],['2012-03-22',0,335],['2012-03-21',0,343],['2012-03-20',0,301]
//        ]);这样折线图会显示出来
     var options = {
     title: '监控'
     };     var chart = new google.visualization.LineChart(document.getElementById('chart_div'));
     chart.draw(data, options);
    }
    </script>
<div id="chart_div" style="width: 900px; height: 500px;"></div>我是把php数组转为json数据，把json数据放到data.addRows（[]）这里，但是不显示，求解