Example use of a simple php based captcha. Requirements: PHP 4.0.3+, GD Image Library, and Session support.
To use this captcha you simply upload captcha.php and add the following line of code to your html in order
to display the captcha image: <img src="captcha.php" alt="captcha" />
You will need to incorporate verification into your site. See 'verify.php' for a simple verification example.
The captcha string is stored in a session variable $_SESSION['captcha'].
To verify captcha information simply compare the data stored in this session variable to the data
entered by your user and submitted in the form. View 'captcha.php' for config options.