1 <?xml version="1.0" encoding="UTF-8"?>
3 <sect1 id="zend.captcha.introduction">
4 <title>Introduction</title>
7 <ulink url="http://en.wikipedia.org/wiki/Captcha">CAPTCHA</ulink>
8 stands for "Completely Automated Public Turing test to tell Computers and Humans
9 Apart"; it is used as a challenge-response to ensure that the individual
10 submitting information is a human and not an automated process. Typically, a
11 captcha is used with form submissions where authenticated users are not
12 necessary, but you want to prevent spam submissions.
16 Captchas can take a variety of forms, including asking logic questions, presenting skewed
17 fonts, and presenting multiple images and asking how they relate.
18 <classname>Zend_Captcha</classname> aims to provide a variety of back ends that may be
19 utilized either standalone or in conjunction with <classname>Zend_Form</classname>.