Version 6 pre-stable
This version of Silverstripe CMS has not yet been given a stable release. See the release roadmap for more information. Go to documentation for the most recent stable version.

Form validation

Before you start implementing custom validation logic, check out validation using symfony/validator constraints and see if there's an existing constraint that can do the heavy lifting for you.

Silverstripe CMS provides server-side form validation out of the box in a couple of ways:

  • Firstly, when a Form is submitted, the FormField::validate() method is called on each FormField instance within the form.
  • Secondly, an instance of Validator sublass can be set on each Form. Validators are implemented as an argument to the Form constructor or through the function setValidator.
namespace App\PageType;

use PageController;
use SilverStripe\Forms\EmailField;
use SilverStripe\Forms\Form;
use SilverStripe\Forms\FormAction;
use SilverStripe\Forms\TextField;
use SilverStripe\Forms\Validation\RequiredFieldsValidator;

class MyFormPageController extends PageController
{
    private static $allowed_actions = [
        'getMyForm',
    ];

    private static $url_handlers = [
        'MyForm' => 'getMyForm',
    ];

    public function getMyForm()
    {
        $fields = FieldList::create(
            TextField::create('Name'),
            // EmailField::validate() will validate the submitted value is a valid email address
            EmailField::create('Email')
        );

        $actions = FieldList::create(
            FormAction::create('doSubmitForm', 'Submit')
        );

        // RequiredFieldsValidator marks the fields 'Name' and 'Email' as required.
        $required = RequiredFieldsValidator::create([
            'Name', 'Email',
        ]);

        // $required can be set as an argument
        $form = Form::create($controller, 'MyForm', $fields, $actions, $required);

        // Or, through a setter.
        $form->setValidator($required);

        return $form;
    }

    public function doSubmitForm($data, $form)
    {
        // ...
    }
}

In this example we will be required to input a value for Name and a valid email address for Email before the doSubmitForm method is called.

Each individual FormField instance is responsible for validating the submitted content through the FormField::validate() method. For example EmailField::validate() checks the field value is a valid email.

Extensions

Extensions applied to FormField, or subclasses, can hook into the validation logic and adjust the results by utilising the updateValidate method. For example, an extension applied to EmailField could look like this:

namespace App\Extension;

use SilverStripe\Core\Extension;
use SilverStripe\Core\Validation\ValidationResult;

class FormFieldValidationExtension extends Extension
{
    protected function updateValidate(ValidationResult $result): void
    {
        if (str_ends_with($this->owner->Value(), '@example.com')) {
            $result->addFieldError(
                $this->getOwner()->Name(),
                'Please provide a valid email address which does not end with @example.com'
            );
        }
    }
}

Validation in FormField subclasses

Subclasses of FormField can define their own version of validate() to provide custom validation rules such as the above example with the Email validation.

namespace App\Form\Field;

use SilverStripe\Core\Validation\ValidationResult;
use SilverStripe\Forms\NumericField;

class CustomNumberField extends NumericField
{
    // ...

    public function validate(): ValidationResult
    {
        $this->beforeExtending('updateValidate', function (ValidationResult $result) {
            if ((int) $this->Value() === 20) {
                $result->addFieldError($this->Name(), 'This value cannot be 20');
            }
        });
        return parent::validate();
    }
}

The validate() method returns a ValidationResult object with any errors added to it, and should contain a useful error message. The validate() method should follow the example above and utilise the $this->beforeExtending('updateValidate', ...) method and be followed by return parent::validate(); in order for code in the parent class to be executed in the correct order.

FieldValidator classes used for FormField validation

Many of the built-in FormField classes use standardised FieldValidator to perform some or all of their validation. For example, the EmailField class uses the both the StringFieldValidator and the EmailFieldValidator for validation.

These are configured via the FormField.field_validators configuration, which you can configure on your own FormField subclasses.

namespace App\Form\Field;

use SilverStripe\Core\Validation\FieldValidation\EmailFieldValidator;
use SilverStripe\Core\Validation\FieldValidation\OptionFieldValidator;
use SilverStripe\Forms\EmailField;

class CustomEmailField extends EmailField
{
    // ...

    private static array $field_validators = [
        // Disable the EmailFieldValidator defined in the parent EmailField by setting it to null
        EmailFieldValidator::class => null,
        // Add an OptionFieldValidator to validate the field value is in a list of allowable values
        OptionFieldValidator::class => ['getAllowableEmails'],
    ];

    public function getAllowableEmails(): array
    {
        return [
            'hello@example.com',
            'welcome@example.com',
        ];
    }
}

Form action validation

ValidationException

At times it's not possible for all validation or recoverable errors to be pre-determined in advance of form submission, such as those generated by the form Validator. Sometimes errors may occur within form action methods, and it is necessary to display errors on the form after initial validation has been performed.

In this case you may throw a ValidationException within your handler, optionally passing it an error message, or a ValidationResult containing the list of errors you wish to display.

E.g.

namespace App\Control;

use SilverStripe\Control\Controller;
use SilverStripe\Core\Validation\ValidationException;

class MyController extends Controller
{
    public function doSave($data, $form)
    {
        $success = $this->sendEmail($data);

        // Example error handling
        if (!$success) {
            throw new ValidationException('Sorry, we could not email to that address');
        }

        // If success
        return $this->redirect($this->Link('success'));
    }
}

Session validation result

An alternative approach to using custom class or an extension is to define the behavior inside the Form's action method. This is less reusable and would not be possible within the CMS or other automated UI but does not rely on creating custom FormField classes or extensions.

namespace App\PageType;

use PageController;
use SilverStripe\Core\Validation\ValidationResult;
use SilverStripe\Forms\EmailField;
use SilverStripe\Forms\FieldList;
use SilverStripe\Forms\Form;
use SilverStripe\Forms\FormAction;
use SilverStripe\Forms\TextField;
use SilverStripe\Security\Member;

class MyFormPageController extends PageController
{
    // ...

    public function getMyForm()
    {
        $fields = FieldList::create(
            TextField::create('Name'),
            EmailField::create('Email')
        );

        $actions = FieldList::create(
            FormAction::create('doSubmitForm', 'Submit')
        );

        $form = Form::create($this, 'MyForm', $fields, $actions);

        return $form;
    }

    public function doSubmitForm($data, $form)
    {
        // At this point, RequiredFieldsValidator->isValid() will have been called already,
        // so we can assume that the values exist. Say we want to make sure that email hasn't already been used.

        $check = Member::get()->filter('Email', $data['Email'])->first();

        if ($check) {
            $validationResult = ValidationResult::create();
            $validationResult->addFieldError('Email', 'This email already exists');
            $form->setSessionValidationResult($validationResult);
            $form->setSessionData($form->getData());
            return $this->redirectBack();
        }


        $form->sessionMessage('You have been added to our mailing list', 'good');

        return $this->redirectBack();
    }
}

Available validators

The Silverstripe framework comes with the following built-in validators:

  • CompositeValidator A container for additional validators. You can implement discrete validation logic in multiple Validator subclasses and apply them all to a given form by putting them inside a CompositeValidator. The CompositeValidator doesn't have perform any validation by itself.
  • RequiredFieldsValidator Validates that fields you declare as "required" have a value.

There are additional validators available in community modules, and you can implement your own validators by subclassing the abstract Validator class.

Validation-exempt actions

In some cases you might need to disable validation for specific actions. For example actions which discard submitted data may not need to check the validity of the posted content.

You can disable validation on individual using one of two methods:

namespace App\PageType;

use PageController;
use SilverStripe\Forms\FieldList;
use SilverStripe\Forms\Form;
use SilverStripe\Forms\FormAction;

class MyFormPageController extends PageController
{
    // ...

    public function getMyForm()
    {
        // ...

        $actions = FieldList::create(
            $action = FormAction::create('doSubmitForm', 'Submit')
        );

        $form = Form::create($this, 'MyForm', $fields, $actions);
        // Disable actions on the form action themselves
        $action->setValidationExempt(true);
        // Alternatively, you can whitelist individual actions on the form object by name
        $form->setValidationExemptActions(['doSubmitForm']);

        return $form;
    }

    // ...
}

Server-side validation messages

If a FormField fails to pass validate() the default error message is returned.

'$Name' is required

Use setCustomValidationMessage to provide a custom message.

use SilverStripe\Forms\TextField;

$field = TextField::create(/* .. */);
$field->setCustomValidationMessage('Whoops, looks like you have missed me!');

JavaScript validation

Although there are no built-in JavaScript validation handlers in Silverstripe CMS, the FormField API is flexible enough to provide the information required in order to plug in custom libraries like Parsley.js. Most of these libraries work on HTML data- attributes or special classes added to each input. For Parsley we can structure the form like.

namespace App\PageType;

use PageController;
use SilverStripe\Forms\Form;

class MyFormPageController extends PageController
{
    // ...

    public function getMyForm()
    {
        // ...

        $form = Form::create($this, 'MyForm', $fields, $actions);
        $form->setAttribute('data-parsley-validate', true);

        $field = $fields->dataFieldByName('Name');
        $field->setAttribute('required', true);
        $field->setAttribute('data-parsley-mincheck', '2');

        return $form;
    }
}

Model validation

An alternative (or additional) approach to validation is to place it directly on the database model. Silverstripe CMS provides a DataObject::validate() method to validate data at the model level. See Data Model Validation.

Validation in the CMS

In the CMS, we're not creating the forms for editing CMS records. The Form instance is generated for us so we cannot call setValidator easily. However, a DataObject can provide its own Validator instance/s through the getCMSCompositeValidator() method. The CMS interfaces such as LeftAndMain, ModelAdmin and GridField will respect the provided Validator/s and handle displaying error and success responses to the user.

Again, custom error messages can be provided through the FormField

namespace App\PageType;

use Page;
use SilverStripe\Forms\FieldList;
use SilverStripe\Forms\TextField;
use SilverStripe\Forms\Validation\CompositeValidator;
use SilverStripe\Forms\Validation\RequiredFieldsValidator;

class MyPage extends Page
{
    private static $db = [
        'MyRequiredField' => 'Text',
    ];

    public function getCMSFields()
    {
        $this->beforeUpdateCMSFields(function (FieldList $fields) {
            $fields->addFieldToTab(
                'Root.Main',
                TextField::create('MyRequiredField')->setCustomValidationMessage('You missed me.')
            );
        });
        return parent::getCMSFields();
    }

    public function getCMSCompositeValidator(): CompositeValidator
    {
        $validator = parent::getCMSCompositeValidator();
        $validator->addValidator(RequiredFieldsValidator::create([
            'MyRequiredField',
        ]));
        return $validator;
    }
}

You can also update the CompositeValidator by creating an Extension and implementing the updateCMSCompositeValidator() method.

RequiredFieldsValidator and whitespace

By default, RequiredFieldsValidator will consider a field with only whitespace as a valid value. You an change this behavior with the allow_whitespace_only global configuration, or on a per-instance basis using setAllowWhitespaceOnly().

# global configuration
SilverStripe\Forms\Validation\RequiredFieldsValidator:
  allow_whitespace_only: false
namespace App\PageType;

use Page;
use SilverStripe\Forms\Validation\CompositeValidator;
use SilverStripe\Forms\Validation\RequiredFieldsValidator;

class MyPage extends Page
{
    // ...

    public function getCMSCompositeValidator(): CompositeValidator
    {
        $validator = parent::getCMSCompositeValidator();
        $requiredFields = RequiredFieldsValidator::create(['MyRequiredField']);
        // per instance configuration, will override global configuration
        $requiredFields->setAllowWhitespaceOnly(false);
        $validator->addValidator($requiredFields);
        return $validator;
    }
}

Related lessons

API documentation

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