使php数组floctcharts兼容，形成Codeigniter

I am designing an app with codeigniter and generating dynamically my arrays and pushing them to my views. Although it seems straitforward I had some problems though.

In my Model function I generate my arrays like this :

foreach ($Q->result_array() as $row)
            {

                $data[]=array(
                              'label'=>$row['students'],
                              'data'=>$row['marks']
                              );         
            }

Then I return $data

In my view I use json_decode like shown here

<script>
  data = <?php echo json_encode($lang);?>;
  data=trim("label", '"');
  //alert(data);
  $.plot($("#graph4"), data, 
    {
        series: {
            pie: { 
                show: true,
                radius: 1,
                label: {
                    show: true,
                    radius: 3/4,
                    formatter: function(label, series){
                        return '<div style="font-size:8pt;text-align:center;padding:2px;color:white;">'+label+'<br/>'+Math.round(series.percent)+'%</div>';
                    },
                    background: { 
                        opacity: 0.5,
                        color: '#000'
                    }
                }
            },
        legend: {
            show: false
        }
});  

</script>

But the json generated is not compatible with flotcharts library, instead of having

[{label:"Mark",data:1},{label:"Jenny",data:1}]

I have

[{"label":"Mark","data":"1"},{"label":"Jenny","data":"1"}]

How can I remove the double quotes so that it can be only applied to labels and not the data

Any help would be appreciated,

Thanks

UPDATE :

For those who will face this problem I solved the problem with regular expression

echo preg_replace('/"([^"]+)"\s*:\s*/', '$1:',json_encode($lang));

You could construct it manually rather than with json functions. I've used something like this in the past, which you can use inside the foreach of your Model:

$data .= '{label:'.$row["students"].',data:'.$row["marks"].'},';

and after the loop:

$data = "[{$data}]";