In order to make sure that the GD installed the following example would be run. The example creates a very simple image using just pure GD calls and outputs an image in PNG format. This could be considered a smoke-test to see that the GD library is available from PHP. Please note that this is an absolute pre-requisite in order for the JpGraph library to work at all.
Store the code snippet below somewhere in the document root and make sure it runs correctly.
$im = @ ImageCreate ( 150, 100)
or die ( "Cannot create a new GD image.");
$background_color = ImageColorAllocate ($im, 255, 255, 255);
$text_color = ImageColorAllocate ($im, 233, 14, 91);
ImageString ($im, 1, 5, 5, "A Simple Text String", $text_color );
header ("Content-type: image/png");
If the above script does not work or some error or warnings are printed on the screen then it is necessary to correct those problems before proceeding with the installation.