/**
  * 图形验证码
  */
 public function captchaAction()
 {
     $captcha = YUN_Captcha::factory($this->config->captcha->driver, $this->config->captcha->options)->generate();
     $this->isload = false;
 }
 /**
  * 单件模式调用方法
  *
  * @return EGP_Captcha
  */
 public static function getInstance()
 {
     null == self::$_instance && (self::$_instance = new self());
     return self::$_instance;
 }