官方网站：http://www.phpcaptcha.org/
下载地址：http://www.phpcaptcha.org/download/
原文地址：http://www.21andy.com/blog/20100417/1886.html
验证码图 片：
<img id="captcha" src="/securimage/securimage_show.php" alt="CAPTCHA Image" />
验证码文 本框：
<input type="text" name="captcha_code" size="10" maxlength="6" />
看不清验证码：
<a href="#" rel="nofollow" target="_blank">Reload Image</a>
后端PHP验 证：
<?php
session_start();
include_once $_SERVER['DOCUMENT_ROOT'] . '/securimage/securimage.php';
$securimage = new Securimage();
if ($securimage->check($_POST['captcha_cod
session_start();
include_once $_SERVER['DOCUMENT_ROOT'] . '/securimage/securimage.php';
$securimage = new Securimage();
if ($securimage->check($_POST['captcha_cod