Pie chart displaying of wedge start/end

[ecopetition]

Hello, I'm trying to work out a method of displaying a pie chart depending on the values in an array by looping for a different value of $i, here's what I have so far:

 

for($i = 0; $i < 11; $i++)
{
	$colour = $i;
	$fraction = ($pie_data[$i]/$total);
	$pie_angle = $fraction*360;
	ImageFilledArc($myImage, 100, 100, 200, 180, STARTANGLE, ENDANGLE, $colour, IMG_ARC_PIE);
}

As you can see I've got fractions, which I'm converting into an angle. However, I can't think of a way to have the startangle and endangle parameters of the ImageFilledArc function depend on all of the previous pie angles, because I'm hoping this pie chart can vary as pieces of data forming each wedge (and each fraction) change.  Can anybody help with this?

 

Thanks so much for your help.

[ecopetition]

[ecopetition]

If any clarification is needed please tell me.