php 饼状图的动态生成代码

<?php
/**
* 使用php内置函数生成饼状图
* by www.jb200.com
*/
$im = imagecreatetruecolor(300,300);

$gray     = imagecolorallocate($im, 0xC0, 0xC0, 0xC0);
$darkgray = imagecolorallocate($im, 0x90, 0x90, 0x90);
$navy     = imagecolorallocate($im, 0x00, 0x00, 0x80);
$darknavy = imagecolorallocate($im, 0x00, 0x00, 0x50);
$red      = imagecolorallocate($im, 0xFF, 0x00, 0x00);
$darkred  = imagecolorallocate($im, 0x90, 0x00, 0x00);

for($i=200;$i>150;$i--){
 imagefilledarc($im,150,$i,300,150,0,45,$darknavy,IMG_ARC_PIE);
 imagefilledarc($im,150,$i,300,150,45,75,$darkgray,IMG_ARC_PIE);
 imagefilledarc($im,150,$i,300,150,75,360,$darkred,IMG_ARC_PIE);
}

imagefilledarc($im,150,150,300,150,0,45,$navy,IMG_ARC_PIE);
imagefilledarc($im,150,150,300,150,45,75,$gray,IMG_ARC_PIE);
imagefilledarc($im,150,150,300,150,75,360,$red,IMG_ARC_PIE);

header('Content-type: image/png');
imagepng($im);
imagedestroy($im);
?>