jpgraph类库引入后写代码出现了问题

require_once ('jpgraph/jpgraph.php');
require_once ('jpgraph/jpgraph_pie.php');
require_once ('jpgraph/jpgraph_pie3d.php');

$browser=array('IE','Chorm','Firefox','safari','other');
$precent=array(58,18,16,6,2);

$graph=new PieGraph(400,300);
$graph->title->Set("浏览器市场额一览图");
$graph->title->SetFont(FF_SIMSUN,FS_BOLD,18);
$graph->title->SetColor("blue");

$p1=new pieplot3D($precent);
$p1->explodeSlice(1);
$p1->setSize(0.4);
$p1->SetCenter(0.45,0.42);
$p1->SetLegends($browser);
$graph->add($p1);
$graph->Stroke();

http://blog.163.com/liujiahng@126/blog/static/170256245201252821922463/