Looking for either a tutorial or manual that is comprehensive to learn how to make line charts in PHP/GD.

Thanks in advance!

Trust me www.php.net is all you'll need. Just look up the functions and use your mind from there. You'll need a little help on the forums but that should be it. This way you don't get into the habit of using just one function for one thing and learn all the functions so you can use more efficient and customized ways to do things.