I have installed pchart as well as Jpgraph on my system but on running their example sites all I get is a blank page. GD has been already installed on my system and I have checked it already. Do I need to change anything in the php.ini file?
You need to enable the GD2 library in PHP. In the PHP.INI look for the line;
extensions=php_gd2.dll
and remove the ; (semi-colon) at the beginning of the line. after you save that file you will need to restart Apache (or whatever you use) for the changes to take effect.
References came from this page; http://www.plus2net.com/php_tutorial/gd-support.php