Introduction - If you have any usage issues, please Google them yourself
How to make a very basic captcha image and validate the form input to make sure the code matches. Does not use sessions of any sort. The image also just uses the built in PHP fonts so no need to load font files. I also put three random lines in the background and add wave effects to the entire image to try and stop bots reading it. The code is heavily commented so most users should be able to see how it works.