如何在php中画饼状图

$image = imagecreate(500, 500);  // 创建 500x500 像素的画布
$background = imagecolorallocate($image, 255, 255, 255); // 设置背景色为白色
imagefill($image, 0, 0, $background);  // 填充背景

$data = [
    'Category A' => 30,
    'Category B' => 50,
    'Category C' => 20
];

$total = array_sum($data);

foreach ($data as $category => $value) {
    $angle = $value / $total * 360;  // 计算角度
    $arc_length = $angle * pi() / 180;  // 计算弧长
}

$start = 0;  // 起始角度

foreach ($data as $category => $value) {
    $angle = $value / $total * 360;  // 计算角度
    imagefilledarc($image, 250, 250, 200, 200, $start, $start + $angle, $color);  // 绘制弧线
    $start += $angle;  // 更新起始角度
}

$colors = [
    'Category A' => imagecolorallocate($image, 255, 0, 0),
    'Category B' => imagecolorallocate($image, 0, 255, 0),
    'Category C' => imagecolorallocate($image, 0, 0, 255)
];

imagettftext($image, 12, 0, 100, 350, $black, 'arial.ttf', 'Category A');

header('Content-Type: image/png');
imagepng($image);