无法用php中的libchart创建图形

I tried to create graph with libchart from array of points but PHP script cant pass this line :

$chart->render("parlament.png");

No errors , but also no graphs rendered.

Any ideas where can be a problem ? Here is code of this script : script

Thanks for every help :)

Libchart generates parlament.png file on site directory. You can echo generated file on your site.