<?php  
  
class Captcha extends CCaptchaAction  
{  
    public function run()  
    {  
        if (isset($_GET[self::REFRESH_GET_VAR])) // AJAX request for regenerating code  
        {  
            $code = $this->getVerifyCode(true);  
            echo CJSON::encode(array(  
                'hash1' => $this->generateValidationHash($code),  
                'hash2' => $this->generateValidationHash(strtolower($code)),  
                // we add a random 'v' parameter so that FireFox can refresh the image  
                // when src attribute of image tag is changed  
                'url' => $this->getController()->createUrl($this->getId(), array('v' => uniqid())),  
            ));  
        } else{  
            $this->renderImage($this->getVerifyCode(true)); //刷新页面时会调用这个，问题就出现在这，他调用  
        }  
        Yii::app()->end();  
    }  
}  
 controller调用
public function actions()  
{  
    return array(  
        // captcha action renders the CAPTCHA image displayed on the contact page  
        'captcha'=>array(  
            'class'=>'Captcha',  
            'maxLength'=>4,  
            'minLength'=>4,  
            'width' => 100  
        ),  
    );  
}  
 html调用
<?php $this->widget('CCaptcha', array('showRefreshButton' => false, 'clickableImage' => true, 'imageOptions' => array('title' => '点击换图', 'style' => 'cursor:pointer;width: 110px; height: 35px;'))); ?>