highcharts多列图表不显示

var id = $("input[id='id1']:checked").val();  
                 getAjaxData(id);                
                //});
            var opt = {
                    chart: {
                        renderTo: 'container4',
                        type: 'column'
                    },
                    title: {
                        text: 'abc',
                        x: -20 //center
                    },
                    
                    xAxis: {
                        categories: []
                          
                    },
                    yAxis: {
                        title: {
                            text: 'Millions'
                        },
                        plotLines: [{
                                value: 0,
                                width: 1,
                                color: '#808080'
                            }]
                    },
                    tooltip: {
                        headerFormat: '<span style="font-size:11px">{series.name}</span><br>',
                        pointFormat: '<span style="color:{point.color}">{point.name}</span>:<b>{point.y}</b> of total<br/>'
                    },
                    plotOptions: {
                        series: {
                            borderWidth: 0,
                            dataLabels: {
                                enabled: true,
                                format: '{point.y}'
                            }
                        }
                    },
                    legend: {
                        itemStyle: {
                
                            fontSize:'10px'
                        },
                        
                        layout: 'vertical',
                        align: 'right',
                        verticalAlign: 'top',
                        
                        floating: true,
                        borderWidth: 1,
                        backgroundColor: ((Highcharts.theme && Highcharts.theme.legendBackgroundColor) || '#FFFFFF'),
                        shadow: true
                        
                    },
                    series: []
                };
                function getAjaxData(id) {
                $.getJSON("file.php", {id: id},function(json) {
                    opt.xAxis.categories = json[0]['data']; 
                    opt.series[0] = json[1];
                    opt.series[1] = json[2];
                    chart = new Highcharts.Chart(opt);
                }); 
           }