From your comment it looks like your php script just cannot find the jpgraph scripts, p.e. wrong path.
Try something like this, if you're using jpgraph as the graph lib of your choice:
$jpgraph_dir = '/your/path/to/your/jpgraph/';
require_once($jpgraph_dir . 'src/jpgraph.php');
If you still receive this error message, your path is just wrong.