JQPlot bar chart OK but pie chart not OK -- using same input data - jqplot

Question

I have the following codes to render a bar chart and a pie chart. Both receives the same set of JSON data from the server as follows:
A: 115.00
B: 55.00
C: 0.00
D: 29.04
For some reasons, the bar chart is able to render it. But nothing appears for the pie chart.
var AjaxDataRenderer = function(url, plot, options) {
var ret;
$.ajax({
async: false, // Needed
url: "getData.php",
dataType:"json",
success: function(data) {
ret = data;
}
});
return ret;
};
var plot = $.jqplot('id-BarChart', [],{
title: "TRIAL",
dataRenderer: AjaxDataRenderer,
seriesDefaults:{
renderer:$.jqplot.BarRenderer,
rendererOptions: {fillToZero: true}
},
series:[{color:'#5FAB78',label:"Actual"}],
legend: {
show: true,
placement: "insideGrid",
rendererOptions: {
textColor: "#FFFFFF",
fontSize: "10pt"
}},
axes: {
xaxis: {
renderer: $.jqplot.CategoryAxisRenderer,
tickRenderer: $.jqplot.CanvasAxisTickRenderer ,
tickOptions: {
angle: -30,
fontSize: '10pt'
}
},
yaxis: {
min: 10,
max: 300,
tickOptions: {
formatString: '$%d'
}
}
}
});
var plot = $.jqplot('id-PieChart', [],{
dataRenderer: AjaxDataRenderer,
title: 'Expenditure pattern for this session',
seriesDefaults: {
renderer: jQuery.jqplot.PieRenderer,
rendererOptions: {
padding: 8,
showDataLabels: true
}
},
});
Anybody can help?

Answer 1

Had done some debugging and found the following works.
This is the PHP codes I have:
$rows = array();
$rows1 = array();
$j = 1;
while($category = mysql_fetch_assoc($allCategories))
{
$current = 0 + $category['ExpenditureCurrent'];
$toDate = 0 + $category['ExpenditureToDate'];
$j += 1;
$rows[] = array($category['Name'], $toDate);
$rows1[] = array($category['Name'], $current);
}
echo json_encode(array($rows,$rows1));
For some reasons, the bar chart works with these:
$current = $category['ExpenditureCurrent'];
$toDate = $category['ExpenditureToDate'];
While the pie chart needs these:
$current = 0 + $category['ExpenditureCurrent'];
$toDate = 0 + $category['ExpenditureToDate'];