System Requirements for Asirra Captcha System - PHP
Asirra (Animal Species Image Recognition for Restricting Access) is a captcha technology developed by Microsoft. This article will explain how it's different from other captcha systems, the benefits of using Asirra, and how to set it up on your PHP-based website.
The following are the system requirements and PHP related functions that must be enabled to use Asirra captcha:
PHP version 5.3.1 (tested to work in this version, though it might work with versions below that number).
Apache web server (not tested in Windows server using PHP).
The use of PHP Globals (variable scope).
There is no need to worry about PHP related specifications, since most of the functions are enabled in most paid hosting accounts. If you are using a free hosting account, your hosting company might disable some of the required functions above, so the Asirra captcha function won't work properly.