验证码事件
onInit
Description
Event called to initialise the captcha
Parameters
$id DOM id of the field that will contain the captcha
Return Value
Boolean True on success, false otherwise
Called in files
libraries/cms/captcha/captcha.php
onDisplay
Description
Parameters
Return Value
Called in files
onCheckAnswer
Description
Parameters
Return Value
Called in files
作者：张敏
原文：http://www.joomlachina.cn/shouce/doc/1916?article_id=1952