未捕获的引用错误-函数没有定义

function generatePieChart(chartData, counter='', diffSeparator=''){     
  var chart;
  var legend;

//chartData = "["+chartData+"]";                        

AmCharts.ready(function () {
    // PIE CHART
    chart = new AmCharts.AmPieChart();
    chart.dataProvider = chartData;
    chart.titleField = "stage";
    chart.valueField = "enquiryCount";
    chart.depth3D = 10;
    chart.angle = 10;

    // LEGEND
    legend = new AmCharts.AmLegend();
    legend.align = "center";
    legend.markerType = "circle";
    chart.balloonText = "[[title]]<br><span style='font-size:14px'><b>[[value]]</b> ([[percents]]%)</span>";
    //chart.addLegend(legend);


    // WRITE
    chart.write("chart_div_"+diffSeparator+"_"+counter);
});


}

generatePieChart(<?=$data?>,'<?=$i?>','o');
function generatePieChart(chartData, counter=''