添加带验证码的登陆：
1.先在模型modules下的LoginForm.php定义一个存储验证码的变量：public $verfyCode；
2.然后在rules()方法里定义：array('verifyCode', 'captcha', 'allowEmpty'=>!CCaptcha::checkRequirements())；
3.然后在对应视图views下的login.php里定义：
<?php if(CCaptcha::checkRequirements()): ?>
<div class="row">
<?php echo $form->labelEx($model,'verifyCode'); ?>
<div>
<?php $this->widget('CCaptcha'); ?>
<?php echo $form->textField($model,'verifyCode'); ?>
</div>
<div class="hint">Please enter the letters as they are shown in the image above.
<br/>Letters are not case-sensitive.</div>
<?php echo $form->error($model,'verifyCode'); ?>
</div>
<?php endif; ?>
4.在login所属的的控制器中加入：
public function actions()
{
return array(
// captcha action renders the CAPTCHA image displayed on the contact page
'captcha'=>array(
'class'=>'CCaptchaAction',
'backColor'=>0xFFFFFF,
),
}