code: public function validate($input, $caseSensitive)
      {
          $code = $this->getVerifyCode();
          $valid = $caseSensitive ? ($input === $code) : strcasecmp($input, $code) === 0;
          $session = Yii::$app->getSession();
          $session->open();
          $name = $this->getSessionKey() . 'count';
          $session[$name] += 1;
          if ($valid || $session[$name] > $this->testLimit && $this->testLimit > 0) {
              $this->getVerifyCode(true);
          }
  
          return $valid;
      }
docs: Validates the input to see if it matches the generated code.
  @param string $input user input
  @param bool $caseSensitive whether the comparison should be case-sensitive
  @return bool whether the input is valid