Chapter 7. Zend_Captcha

Table of Contents

7.1. Introduction
7.2. Captcha Operation
7.3. CAPTCHA Adapters
7.3.1. Zend_Captcha_Word
7.3.2. Zend_Captcha_Dumb
7.3.3. Zend_Captcha_Figlet
7.3.4. Zend_Captcha_Image
7.3.5. Zend_Captcha_ReCaptcha

7.1. Introduction

CAPTCHA stands for "Completely Automated Public Turing test to tell Computers and Humans Apart"; it is used as a challenge-response to ensure that the individual submitting information is a human and not an automated process. Typically, a captcha is used with form submissions where authenticated users are not necessary, but you want to prevent spam submissions.

Captchas can take a variety of forms, including asking logic questions, presenting skewed fonts, and presenting multiple images and asking how they relate. Zend_Captcha aims to provide a variety of back ends that may be utilized either standalone or in conjunction with Zend_Form.