Thats enough about the why (and the why not). How do we implement a practical captcha system?
There are many dynamic web programming languages in the world, and I can’t cover all of them in every article. Here I’ll assume you are using PHP. If you’re not using PHP, you should consider it! PHP is the most popular tool of its kind, and it runs on all major web servers. I have written a simple captcha system in PHP which you can use on your own site. It’s easy to set up and extremely easy to plug into your own PHP code. And you can try a live demo here. The only catches are: 1. Your server’s PHP must include the GD library, with support for JPEG and FreeType (TrueType font output). If it does, you will see that mentioned in your phpinfo page. If not, complain to your web host— they aren’t doing a good job if they still don’t give you this widely expected feature in 2007. 2. If you don’t mind the Bitstream Vera font or the sound of my voice, great! If you aren’t crazy about those two things, you’ll need to provide your own recordings of the letters of the alphabet and your own True
