Forms are relatively easy to create. At the bare minimum, each element or fieldset requires a name; typically, you’ll also provide some attributes to hint to the view layer how it might render the item. The form itself will also typically compose an InputFilter– which you can also conveniently create directly in the form via a factory. Individual elements can hint as to what defaults to use when generating a related input for the input filter.
Form validation is as easy as providing an array of data to the setData() method. If you want to simplify your work even more, you can bind an object to the form; on successful validation, it will be populated from the validated values.
If nothing else, you can simply start creating elements, fieldsets, and forms and wiring them together.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 | use Zend\Captcha;
use Zend\Form\Element;
use Zend\Form\Fieldset;
use Zend\Form\Form;
use Zend\InputFilter\Input;
use Zend\InputFilter\InputFilter;
$name = new Element('name');
$name->setLabel('Your name');
$name->setAttributes(array(
'type' => 'text'
));
$email = new Element\Email('email');
$email->setLabel('Your email address');
$subject = new Element('subject');
$subject->setLabel('Subject');
$subject->setAttributes(array(
'type' => 'text'
));
$message = new Element\Textarea('message');
$message->setLabel('Message');
$captcha = new Element\Captcha('captcha');
$captcha->setCaptcha(new Captcha\Dumb());
$captcha->setLabel('Please verify you are human');
$csrf = new Element\Csrf('security');
$send = new Element('send');
$send->setValue('Submit');
$send->setAttributes(array(
'type' => 'submit'
));
$form = new Form('contact');
$form->add($name);
$form->add($email);
$form->add($subject);
$form->add($message);
$form->add($captcha);
$form->add($csrf);
$form->add($send);
$nameInput = new Input('name');
// configure input... and all others
$inputFilter = new InputFilter();
// attach all inputs
$form->setInputFilter($inputFilter);
|
As a demonstration of fieldsets, let’s alter the above slightly. We’ll create two fieldsets, one for the sender information, and another for the message details.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | $sender = new Fieldset('sender');
$sender->add($name);
$sender->add($email);
$details = new Fieldset('details');
$details->add($subject);
$details->add($message);
$form = new Form('contact');
$form->add($sender);
$form->add($details);
$form->add($captcha);
$form->add($csrf);
$form->add($send);
|
Regardless of approach, as you can see, this can be tedious.
You can create the entire form, and input filter, using the Factory. This is particularly nice if you want to store your forms as pure configuration; you can simply pass the configuration to the factory and be done.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 | use Zend\Form\Factory;
$factory = new Factory();
$form = $factory->createForm(array(
'hydrator' => 'Zend\Stdlib\Hydrator\ArraySerializable',
'elements' => array(
array(
'spec' => array(
'name' => 'name',
'options' => array(
'label' => 'Your name',
),
'type' => 'Text',
)
),
array(
'spec' => array(
'type' => 'Zend\Form\Element\Email',
'name' => 'email',
'options' => array(
'label' => 'Your email address',
)
),
),
array(
'spec' => array(
'name' => 'subject',
'options' => array(
'label' => 'Subject',
),
'type' => 'Text',
),
),
array(
'spec' => array(
'type' => 'Zend\Form\Element\Textarea',
'name' => 'message',
'options' => array(
'label' => 'Message',
)
),
),
array(
'spec' => array(
'type' => 'Zend\Form\Element\Captcha',
'name' => 'captcha',
'options' => array(
'label' => 'Please verify you are human.',
'captcha' => array(
'class' => 'Dumb',
),
),
),
),
array(
'spec' => array(
'type' => 'Zend\Form\Element\Csrf',
'name' => 'security',
),
),
array(
'spec' => array(
'name' => 'send',
'type' => 'Submit',
'attributes' => array(
'value' => 'Submit',
),
),
),
),
/* If we had fieldsets, they'd go here; fieldsets contain
* "elements" and "fieldsets" keys, and potentially a "type"
* key indicating the specific FieldsetInterface
* implementation to use.
'fieldsets' => array(
),
*/
// Configuration to pass on to
// Zend\InputFilter\Factory::createInputFilter()
'input_filter' => array(
/* ... */
),
));
|
If we wanted to use fieldsets, as we demonstrated in the previous example, we could do the following:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 | use Zend\Form\Factory;
$factory = new Factory();
$form = $factory->createForm(array(
'hydrator' => 'Zend\Stdlib\Hydrator\ArraySerializable',
'fieldsets' => array(
array(
'spec' => array(
'name' => 'sender',
'elements' => array(
array(
'spec' => array(
'name' => 'name',
'options' => array(
'label' => 'Your name',
),
'type' => 'Text'
),
),
array(
'spec' => array(
'type' => 'Zend\Form\Element\Email',
'name' => 'email',
'options' => array(
'label' => 'Your email address',
),
),
),
),
),
),
array(
'spec' => array(
'name' => 'details',
'elements' => array(
array(
'spec' => array(
'name' => 'subject',
'options' => array(
'label' => 'Subject',
),
'type' => 'Text',
),
),
array(
'spec' => array(
'name' => 'message',
'type' => 'Zend\Form\Element\Textarea',
'options' => array(
'label' => 'Message',
),
),
),
),
),
),
),
'elements' => array(
array(
'spec' => array(
'type' => 'Zend\Form\Element\Captcha',
'name' => 'captcha',
'options' => array(
'label' => 'Please verify you are human. ',
'captcha' => array(
'class' => 'Dumb',
),
),
),
),
array(
'spec' => array(
'type' => 'Zend\Form\Element\Csrf',
'name' => 'security',
),
),
array(
'spec' => array(
'name' => 'send',
'type' => 'Submit',
'attributes' => array(
'value' => 'Submit',
),
),
),
),
// Configuration to pass on to
// Zend\InputFilter\Factory::createInputFilter()
'input_filter' => array(
/* ... */
),
));
|
Note that the chief difference is nesting; otherwise, the information is basically the same.
The chief benefits to using the Factory are allowing you to store definitions in configuration, and usage of significant whitespace.
The default Form implementation is backed by the Factory. This allows you to extend it, and define your form internally. This has the benefit of allowing a mixture of programmatic and factory-backed creation, as well as defining a form for re-use in your application.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 | namespace Contact;
use Zend\Captcha\AdapterInterface as CaptchaAdapter;
use Zend\Form\Element;
use Zend\Form\Form;
class ContactForm extends Form
{
protected $captcha;
public function __construct(CaptchaAdapter $captcha)
{
$this->captcha = $captcha;
// add() can take either an Element/Fieldset instance,
// or a specification, from which the appropriate object
// will be built.
$this->add(array(
'name' => 'name',
'options' => array(
'label' => 'Your name',
),
'type' => 'Text',
));
$this->add(array(
'type' => 'Zend\Form\Element\Email',
'name' => 'email',
'options' => array(
'label' => 'Your email address',
),
));
$this->add(array(
'name' => 'subject',
'options' => array(
'label' => 'Subject',
),
'type' => 'Text',
));
$this->add(array(
'type' => 'Zend\Form\Element\Textarea',
'name' => 'message',
'options' => array(
'label' => 'Message',
),
));
$this->add(array(
'type' => 'Zend\Form\Element\Captcha',
'name' => 'captcha',
'options' => array(
'label' => 'Please verify you are human.',
'captcha' => $this->captcha,
),
));
$this->add(new Element\Csrf('security'));
$this->add(array(
'name' => 'send',
'type' => 'Submit',
'attributes' => array(
'value' => 'Submit',
),
));
// We could also define the input filter here, or
// lazy-create it in the getInputFilter() method.
}
}
|
You’ll note that this example, the elements are added in the constructor. This is done to allow altering and/or configuring either the form or input filter factory instances, which could then have bearing on how elements, inputs, etc. are created. In this case, it also allows injection of the CAPTCHA adapter, allowing us to configure it elsewhere in our application and inject it into the form.
Validating forms requires three steps. First, the form must have an input filter attached. Second, you must inject the data to validate into the form. Third, you validate the form. If invalid, you can retrieve the error messages, if any.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | $form = new Contact\ContactForm();
// If the form doesn't define an input filter by default, inject one.
$form->setInputFilter(new Contact\ContactFilter());
// Get the data. In an MVC application, you might try:
$data = $request->getPost(); // for POST data
$data = $request->getQuery(); // for GET (or query string) data
$form->setData($data);
// Validate the form
if ($form->isValid()) {
$validatedData = $form->getData();
} else {
$messages = $form->getMessages();
}
|
You can get the raw data if you want, by accessing the composed input filter.
1 2 3 4 | $filter = $form->getInputFilter();
$rawValues = $filter->getRawValues();
$nameRawValue = $filter->getRawValue('name');
|
Often, you’ll create elements that you expect to behave in the same way on each usage, and for which you’ll want specific filters or validation as well. Since the input filter is a separate object, how can you achieve these latter points?
Because the default form implementation composes a factory, and the default factory composes an input filter factory, you can have your elements and/or fieldsets hint to the input filter. If no input or input filter is provided in the input filter for that element, these hints will be retrieved and used to create them.
To do so, one of the following must occur. For elements, they must implement Zend\InputFilter\InputProviderInterface, which defines a getInputSpecification() method; for fieldsets, they must implement Zend\InputFilter\InputFilterProviderInterface, which defines a getInputFilterSpecification() method.
In the case of an element, the getInputSpecification() method should return data to be used by the input filter factory to create an input. Every HTML5 (email, url, color…) elements have a built-in element that use this logic. For instance, here is how the Zend\Form\Element\Color element is defined:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 | namespace Zend\Form\Element;
use Zend\Form\Element;
use Zend\InputFilter\InputProviderInterface;
use Zend\Validator\Regex as RegexValidator;
use Zend\Validator\ValidatorInterface;
class Color extends Element implements InputProviderInterface
{
/**
* Seed attributes
*
* @var array
*/
protected $attributes = array(
'type' => 'color',
);
/**
* @var ValidatorInterface
*/
protected $validator;
/**
* Get validator
*
* @return ValidatorInterface
*/
protected function getValidator()
{
if (null === $this->validator) {
$this->validator = new RegexValidator('/^#[0-9a-fA-F]{6}$/');
}
return $this->validator;
}
/**
* Provide default input rules for this element
*
* Attaches an email validator.
*
* @return array
*/
public function getInputSpecification()
{
return array(
'name' => $this->getName(),
'required' => true,
'filters' => array(
array('name' => 'Zend\Filter\StringTrim'),
array('name' => 'Zend\Filter\StringToLower'),
),
'validators' => array(
$this->getValidator(),
),
);
}
}
|
The above would hint to the input filter to create and attach an input named after the element, marking it as required, and giving it a StringTrim and StringToLower filters and a Regex validator. Note that you can either rely on the input filter to create filters and validators, or directly instantiate them.
For fieldsets, you do very similarly; the difference is that getInputFilterSpecification() must return configuration for an input filter.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 | namespace Contact\Form;
use Zend\Form\Fieldset;
use Zend\InputFilter\InputFilterProviderInterface;
use Zend\Validator;
class SenderFieldset extends Fieldset implements InputFilterProviderInterface
{
public function getInputFilterSpecification()
{
return array(
'name' => array(
'required' => true,
'filters' => array(
array('name' => 'Zend\Filter\StringTrim'),
),
),
'email' => array(
'required' => true,
'filters' => array(
array('name' => 'Zend\Filter\StringTrim'),
),
'validators' => array(
new Validator\EmailAddress(),
),
),
);
}
}
|
Specifications are a great way to make forms, fieldsets, and elements re-usable trivially in your applications. In fact, the Captcha and Csrf elements define specifications in order to ensure they can work without additional user configuration!
Note
If you set custom input filter specification either in getInputSpecification() or in getInputFilterSpecification(), the Zend\InputFilter\InputInterface set for that specific field is reset to the default Zend\InputFilter\Input.
Some form elements may need a particular input filter, like Zend\Form\Element\File: in this case it’s mandatory to specify the type key in your custom specification to match the original one (in ex. for the file element it’s Zend\InputFilter\FileInput).
As noted in the intro, forms in Zend Framework bridge the domain model and the view layer. Let’s see that in action.
When you bind() an object to the form, the following happens:
This is easier to understand in practice.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | $contact = new ArrayObject;
$contact['subject'] = '[Contact Form] ';
$contact['message'] = 'Type your message here';
$form = new Contact\ContactForm;
$form->bind($contact); // form now has default values for
// 'subject' and 'message'
$data = array(
'name' => 'John Doe',
'email' => 'j.doe@example.tld',
'subject' => '[Contact Form] \'sup?',
);
$form->setData($data);
if ($form->isValid()) {
// $contact now looks like:
// array(
// 'name' => 'John Doe',
// 'email' => 'j.doe@example.tld',
// 'subject' => '[Contact Form] \'sup?',
// 'message' => 'Type your message here',
// )
// only as an ArrayObject
}
|
When an object is bound to the form, calling getData() will return that object by default. If you want to return an associative array instead, you can pass the FormInterface::VALUES_AS_ARRAY flag to the method.
1 2 | use Zend\Form\FormInterface;
$data = $form->getData(FormInterface::VALUES_AS_ARRAY);
|
Zend Framework ships several standard hydrators, and implementation is as simple as implementing Zend\Stdlib\Hydrator\HydratorInterface, which looks like this:
1 2 3 4 5 6 7 8 | namespace Zend\Stdlib\Hydrator;
interface HydratorInterface
{
/** @return array */
public function extract($object);
public function hydrate(array $data, $object);
}
|
As noted previously, forms are meant to bridge the domain model and view layer. We’ve discussed the domain model binding, but what about the view?
The form component ships a set of form-specific view helpers. These accept the various form objects, and introspect them in order to generate markup. Typically, they will inspect the attributes, but in special cases, they may look at other properties and composed objects.
When preparing to render, you will likely want to call prepare(). This method ensures that certain injections are done, and will likely in the future munge names to allow for scoped[array][notation].
The simplest view helpers available are Form, FormElement, FormLabel, and FormElementErrors. Let’s use them to display the contact form.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 | <?php
// within a view script
$form = $this->form;
$form->prepare();
// Assuming the "contact/process" route exists...
$form->setAttribute('action', $this->url('contact/process'));
// Set the method attribute for the form
$form->setAttribute('method', 'post');
// Get the form label plugin
$formLabel = $this->plugin('formLabel');
// Render the opening tag
echo $this->form()->openTag($form);
?>
<div class="form_element">
<?php
$name = $form->get('name');
echo $formLabel->openTag() . $name->getOption('label');
echo $this->formInput($name);
echo $this->formElementErrors($name);
echo $formLabel->closeTag();
?></div>
<div class="form_element">
<?php
$subject = $form->get('subject');
echo $formLabel->openTag() . $subject->getOption('label');
echo $this->formInput($subject);
echo $this->formElementErrors($subject);
echo $formLabel->closeTag();
?></div>
<div class="form_element">
<?php
$message = $form->get('message');
echo $formLabel->openTag() . $message->getOption('label');
echo $this->formTextarea($message);
echo $this->formElementErrors($message);
echo $formLabel->closeTag();
?></div>
<div class="form_element">
<?php
$captcha = $form->get('captcha');
echo $formLabel->openTag() . $captcha->getOption('label');
echo $this->formCaptcha($captcha);
echo $this->formElementErrors($captcha);
echo $formLabel->closeTag();
?></div>
<?php echo $this->formElement($form->get('security')) ?>
<?php echo $this->formElement($form->get('send')) ?>
<?php echo $this->form()->closeTag() ?>
|
There are a few things to note about this. First, to prevent confusion in IDEs and editors when syntax highlighting, we use helpers to both open and close the form and label tags. Second, there’s a lot of repetition happening here; we could easily create a partial view script or a composite helper to reduce boilerplate. Third, note that not all elements are created equal – the CSRF and submit elements don’t need labels or error messages necessarily. Finally, note that the FormElement helper tries to do the right thing – it delegates actual markup generation to other view helpers; however, it can only guess what specific form helper to delegate to based on the list it has. If you introduce new form view helpers, you’ll need to extend the FormElement helper, or create your own.
However, your view files can quickly become long and repetitive to write. While we do not currently provide a single-line form view helper (as this reduces the form customization), the simplest and most recommended way to render your form is by using the FormRow view helper. This view helper automatically renders a label (if present), the element itself using the FormElement helper, as well as any errors that could arise. Here is the previous form, rewritten to take advantage of this helper :
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 | <?php
// within a view script
$form = $this->form;
$form->prepare();
// Assuming the "contact/process" route exists...
$form->setAttribute('action', $this->url('contact/process'));
// Set the method attribute for the form
$form->setAttribute('method', 'post');
// Render the opening tag
echo $this->form()->openTag($form);
?>
<div class="form_element">
<?php
$name = $form->get('name');
echo $this->formRow($name);
?></div>
<div class="form_element">
<?php
$subject = $form->get('subject');
echo $this->formRow($subject);
?></div>
<div class="form_element">
<?php
$message = $form->get('message');
echo $this->formRow($message);
?></div>
<div class="form_element">
<?php
$captcha = $form->get('captcha');
echo $this->formRow($captcha);
?></div>
<?php echo $this->formElement($form->get('security')) ?>
<?php echo $this->formElement($form->get('send')) ?>
<?php echo $this->form()->closeTag() ?>
|
Note that FormRow helper automatically prepends the label. If you want it to be rendered after the element itself, you can pass an optional parameter to the FormRow view helper :
1 2 3 4 5 | <div class="form_element">
<?php
$name = $form->get('name');
echo $this->formRow($name, **'append'**);
?></div>
|
HTML5 brings a lot of exciting features, one of them being a simplified client form validations. Adding HTML5 attributes is simple as you just need to add specify the attributes. However, please note that adding those attributes does not automatically add Zend validators to the form’s input filter. You still need to manually add them.
1 2 3 4 5 6 7 8 9 10 11 | $form->add(array(
'name' => 'phoneNumber',
'options' => array(
'label' => 'Your phone number'
),
'attributes' => array(
'type' => 'tel'
'required' => 'required',
'pattern' => '^0[1-68]([-. ]?[0-9]{2}){4}$'
)
));
|
View helpers will automatically render those attributes, and hence allowing modern browsers to perform automatic validation.
Note
Although client validation is nice from a user experience point of view, it has to be used in addition with server validation, as client validation can be easily fooled.
Sometimes you want to validate only a subset of form elements. As an example, let’s say we’re re-using our contact form over a web service; in this case, the Csrf, Captcha, and submit button elements are not of interest, and shouldn’t be validated.
Zend\Form provides a proxy method to the underlying InputFilter‘s setValidationGroup() method, allowing us to perform this operation.
1 2 3 4 5 6 | $form->setValidationGroup('name', 'email', 'subject', 'message');
$form->setData($data);
if ($form->isValid()) {
// Contains only the "name", "email", "subject", and "message" values
$data = $form->getData();
}
|
If you later want to reset the form to validate all, simply pass the FormInterface::VALIDATE_ALL flag to the setValidationGroup() method.
1 2 | use Zend\Form\FormInterface;
$form->setValidationGroup(FormInterface::VALIDATE_ALL);
|
When your form contains nested fieldsets, you can use an array notation to validate only a subset of the fieldsets :
1 2 3 4 5 6 7 8 9 10 11 12 | $form->setValidationGroup(array(
'profile' => array(
'firstname',
'lastname'
)
));
$form->setData($data);
if ($form->isValid()) {
// Contains only the "firstname" and "lastname" values from the
// "profile" fieldset
$data = $form->getData();
}
|
Creating a complete forms solution can often be tedious: you’ll create some domain model object, an input filter for validating it, a form object for providing a representation for it, and potentially a hydrator for mapping the form elements and fieldsets to the domain model. Wouldn’t it be nice to have a central place to define all of these?
Annotations allow us to solve this problem. You can define the following behaviors with the shipped annotations in Zend\Form:
To use annotations, you simply include them in your class and/or property docblocks. Annotation names will be resolved according to the import statements in your class; as such, you can make them as long or as short as you want depending on what you import.
Note
Form annotations require Doctrine\Common, which contains an annotation parsering engine. The simplest way to install Doctrine\Common is if you are using Composer; simply update your composer.json and add the following line to the require section:
1 | "doctrine/common": ">=2.1",
|
Then run php composer.phar update to install the dependency.
If you’re not using Composer, visit the Doctrine project website for more details on installation.
Here’s a simple example.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | use Zend\Form\Annotation;
/**
* @Annotation\Name("user")
* @Annotation\Hydrator("Zend\Stdlib\Hydrator\ObjectProperty")
*/
class User
{
/**
* @Annotation\Exclude()
*/
public $id;
/**
* @Annotation\Filter({"name":"StringTrim"})
* @Annotation\Validator({"name":"StringLength", "options":{"min":1, "max":25}})
* @Annotation\Validator({"name":"Regex", "options":{"pattern":"/^[a-zA-Z][a-zA-Z0-9_-]{0,24}$/"}})
* @Annotation\Attributes({"type":"text"})
* @Annotation\Options({"label":"Username:"})
*/
public $username;
/**
* @Annotation\Type("Zend\Form\Element\Email")
* @Annotation\Options({"label":"Your email address:"})
*/
public $email;
}
|
The above will hint to the annotation build to create a form with name “user”, which uses the hydrator Zend\Stdlib\Hydrator\ObjectProperty. That form will have two elements, “username” and “email”. The “username” element will have an associated input that has a StringTrim filter, and two validators: a StringLength validator indicating the username is between 1 and 25 characters, and a Regex validator asserting it follows a specific accepted pattern. The form element itself will have an attribute “type” with value “text” (a text element), and a label “Username:”. The “email” element will be of type Zend\Form\Element\Email, and have the label “Your email address:”.
To use the above, we need Zend\Form\Annotation\AnnotationBuilder:
1 2 3 4 | use Zend\Form\Annotation\AnnotationBuilder;
$builder = new AnnotationBuilder();
$form = $builder->createForm('User');
|
At this point, you have a form with the appropriate hydrator attached, an input filter with the appropriate inputs, and all elements.
Note
You’re not done
In all likelihood, you’ll need to add some more elements to the form you construct. For example, you’ll want a submit button, and likely a CSRF-protection element. We recommend creating a fieldset with common elements such as these that you can then attach to the form you build via annotations.
The source code of this file is hosted on GitHub. Everyone can update and fix errors in this document with few clicks - no downloads needed.