captcha

a completely automated public turing test to tell computers and humans apart.

basically, this generates an image with distorted text in it. a human should be able to figure out what is written, but a program won't. i use it to make sure bots don't post ads in the comments part of my website. to use it, you must have a readable directory of truetype fonts, and only truetype fonts. then set the variable $fontFolder to that path. next, all you have to do is set up a form and handling script to ask the user to enter the text and then compare what was entered to $_SESSION["captchastr"]. make sure to kill the session after authentication is complete by using session_destroy(). without doing that, an authenticated session could be reused, thereby defeating the whole purpose.

this code requires php 5 (or greater) and gd2. it's been tested only with apache webserver, but i don't see why it wouldn't run on iis.

Download: captcha