This is the opposite of the isValid method

@return bool
351482
public function hasErrors() : bool
    {
        if (false === $this->validated) {
            $this->validate();
        }
        return (count($this->validation_errors) > 0);
    }
992476
public function isValid()
    {
        if (empty($this->jsonrpc)) {
            return false;
        }

        if (empty($this->method) || !is_string($this->method)) {
            return false;
        }

        if (!empty($this->params) && !is_array($this->params)) {
            return false;
        }

        return true;
    }
806001
protected function isValid()
    {
        if (!$this->request->ajax()) {
            return false;
        }
        $search = $this->request->input('search');
        if (!is_string($search) or strlen($this->request->input('search')) <= 0) {
            return false;
        }
        $token = $this->request->header('search-protection');
        if (!$this->validateToken($token)) {
            return false;
        }
        return true;
    }
1044063
public function isValid() {
        if ($this->isValid === null) $this->isValid = $this->validate();
        return $this->isValid;
    }
1266758
public function valid()
    {
        $key = isset($this->items[$this->pos]) ? $this->items[$this->pos] : null;
        return ($key !== null && $key !== false);
    }
1055764
public function isValid()
    {
        $row = $this->getActulRow();

        if ($row[$this->column] >= $this->min  && $row[$this->column] <= $this->max) {
            return true;
        }
        return false;
    }
394040
public function valid()
	{
		if( $this->next() )
			return TRUE;
		if( is_resource( $this->filePointer ) )
			fclose( $this->filePointer );
		return FALSE;
	}
11653
public function isValid() {
        $valid = parent::isValid();
        if (!filter_var($this->getValue(), FILTER_VALIDATE_EMAIL)) {
            $valid = false;
        }
        
        return $valid;
    }
53917
public function isValid()
	{
	  	// Skip without submission
		if (strtoupper($_SERVER['REQUEST_METHOD']) !== 'POST') {

			return FALSE;

		} else {

			$captchaChallenge = isset($_POST['recaptcha_challenge_field'])
				? $this->_sanitizeField($_POST['recaptcha_challenge_field'])
				: NULL;

			$captchaResponse  = isset($_POST['recaptcha_response_field'])
				? $this->_sanitizeField($_POST['recaptcha_response_field'])
				: NULL;
		 	// Skip empty submission
			if ( strlen($captchaChallenge) == 0 || strlen($captchaResponse) == 0 ) {
				$this->setError('incorrect-captcha-sol');
				return FALSE;
			}

			$data = array(
				'privatekey' => $this->_privateKey,
				'remoteip'   => $this->_remoteIp(),
				'challenge'  => $captchaChallenge,
				'response'   => $captchaResponse
				);

			$result = $this->_postHttpChallenge($data);

			if ( $result['isvalid'] === "true") {
				return TRUE;

			} else {
				$this->setError($result['error']);
			}
			return FALSE;
		}
	}
1218933
public function isActionValid ()
	{
		return substr ($this->action, 0, 2) !== '__' && !in_array (strtolower ($this->action), $this->invalidActions);
	}
414324
public function is_valid() {
        $ret = false;

        if (is_null($this->deleteInsteadOfAppend) === false && is_null($this->subscriberIds) === false &&
            is_null($this->emails) === false
        ) {
            $ret = true;
        }

        return $ret;
    }
84709
public function isValid()
    {
        $localSign = generate_sign($this->getNotify()->except('sign')->all(), $this->merchant->key, 'md5');

        return $localSign === $this->getNotify()->get('sign');
    }
176826
public function isValid() {

		$params = $this -> getParameters();

		if(false === isset($params[0])) {
			return trigger_error(sprintf('Missing argument 1 for %s', __METHOD__), E_USER_ERROR);
		}

		if(false === is_string($params[0])) {
			return trigger_error(sprintf('Argument 1 passed to %s() must be of the type string, "%s" given', __METHOD__, gettype($params[0])), E_USER_ERROR);
		}

		foreach($this -> getValues() as $fieldname => $value) {

			if($fieldname == $params[0]) {
				return $value == $this -> getValue();
			}
		}

		return true;
	}
238102
public function isValid()
    {
        $timeLimit = $this->timer->getSeconds();

        if ($timeLimit > $this->limit) {
            $this->timer->start($timeLimit - $this->limit);

            return true;
        }

        return false;
    }
1066364
public function isValid()
    {
        if ($this->valid === null) {
            $this->valid = true;

            if (sizeof($this->validators) > 0) {
                foreach ($this->validators as $validator) {
                    if (!$validator->isValid()) {
                        $this->errors[] = $validator->getErrorMessage();
                        $this->valid = false;
                    }
                }
            }
        }

        return $this->valid;
    }
946598
public function isValid() : bool
    {
        $this->validate();

        if ($this->hasErrors()) {
            return false;
        }

        foreach ($this->components as $component) {
            if ($component->hasErrors()) {
                return false;
            }
        }

        return true;
    }
91737
public function isValid()
    {
        if(empty($this->token) || empty($this->payerId) || is_null($this->_paymentDetails)) {
            return false;
        }

        $valid = true;
        foreach($this->_paymentDetails as $detail) {
            if(empty($detail)) {
                $valid = false;
                break;
            }

            $amt = $detail->getAmt();

            if(empty($amt)) {
                $valid = false;
                break;
            }
        }

        return $valid;
    }