# Class yii\captcha\Captcha

Inheritance | yii\captcha\Captcha » yii\widgets\InputWidget » yii\base\Widget » yii\base\Component » yii\base\BaseObject
Implements | yii\base\Configurable, yii\base\ViewContextInterface
Available since version | 2.0
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/captcha/Captcha.php

Captcha renders a CAPTCHA image and an input field that takes user-entered verification code.

Captcha is used together with yii\captcha\CaptchaAction to provide CAPTCHA - a way of preventing website spamming.

The image element rendered by Captcha will display a CAPTCHA image generated by an action whose route is specified by $captchaAction. This action must be an instance of yii\captcha\CaptchaAction.

When the user clicks on the CAPTCHA image, it will cause the CAPTCHA image to be refreshed with a new CAPTCHA.

You may use yii\captcha\CaptchaValidator to validate the user input matches the current CAPTCHA verification code.

The following example shows how to use this widget with a model attribute:

    echo Captcha::widget([
        'model' => $model,
        'attribute' => 'captcha',
    ]);

The following example will use the name property instead:

    echo Captcha::widget([
        'name' => 'captcha',
    ]);

You can also use this widget in an ActiveForm using the widget() method, for example like this:

    <?= $form->field($model, 'captcha')->widget(\yii\captcha\Captcha::classname(), [
        // configure additional widget properties here
    ]) ?>

## Public Properties

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Property | Type | Description | Defined By
--- | --- | --- | ---
$attribute | string | The model attribute that this widget is associated with. | yii\widgets\InputWidget
$autoIdPrefix | string | The prefix to the automatically generated widget IDs. | yii\base\Widget
$behaviors | yii\base\Behavior[] | List of behaviors attached to this component. This property is read-only. | yii\base\Component
$captchaAction | string|array | The route of the action that generates the CAPTCHA images. | yii\captcha\Captcha
$counter | integer | A counter used to generate $id for widgets. | yii\base\Widget
$field | yii\widgets\ActiveField | Active input field, which triggers this widget rendering. | yii\widgets\InputWidget
$id | string|null | ID of the widget. Note that the type of this property differs in getter and setter. See getId() and setId() for details. | yii\base\Widget
$imageOptions | array | HTML attributes to be applied to the CAPTCHA image tag. | yii\captcha\Captcha
$model | yii\base\Model | The data model that this widget is associated with. | yii\widgets\InputWidget
$name | string | The input name. | yii\widgets\InputWidget
$options | array | The HTML attributes for the input tag. | yii\captcha\Captcha
$stack | yii\base\Widget[] | The widgets that are currently being rendered (not ended). | yii\base\Widget
$template | string | The template for arranging the CAPTCHA image tag and the text input tag. | yii\captcha\Captcha
$value | string | The input value. | yii\widgets\InputWidget
$view | yii\web\View | The view object that can be used to render views or view files. Note that the type of this property differs in getter and setter. See getView() and setView() for details. | yii\base\Widget
$viewPath | string | The directory containing the view files for this widget. This property is read-only. | yii\base\Widget

## Public Methods

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Method | Description | Defined By
--- | --- | ---
__call() | Calls the named method which is not a class method. | yii\base\Component
__clone() | This method is called after the object is created by cloning an existing one. | yii\base\Component
__construct() | Constructor. | yii\base\BaseObject
__get() | Returns the value of a component property. | yii\base\Component
__isset() | Checks if a property is set, i.e. defined and not null. | yii\base\Component
__set() | Sets the value of a component property. | yii\base\Component
__unset() | Sets a component property to be null. | yii\base\Component
afterRun() | This method is invoked right after a widget is executed. | yii\base\Widget
attachBehavior() | Attaches a behavior to this component. | yii\base\Component
attachBehaviors() | Attaches a list of behaviors to the component. | yii\base\Component
beforeRun() | This method is invoked right before the widget is executed. | yii\base\Widget
begin() | Begins a widget. | yii\base\Widget
behaviors() | Returns a list of behaviors that this component should behave as. | yii\base\Component
canGetProperty() | Returns a value indicating whether a property can be read. | yii\base\Component
canSetProperty() | Returns a value indicating whether a property can be set. | yii\base\Component
checkRequirements() | Checks if there is graphic extension available to generate CAPTCHA images. | yii\captcha\Captcha
className() | Returns the fully qualified name of this class. | yii\base\BaseObject
detachBehavior() | Detaches a behavior from the component. | yii\base\Component
detachBehaviors() | Detaches all behaviors from the component. | yii\base\Component
end() | Ends a widget. | yii\base\Widget
ensureBehaviors() | Makes sure that the behaviors declared in behaviors() are attached to this component. | yii\base\Component
getBehavior() | Returns the named behavior object. | yii\base\Component
getBehaviors() | Returns all behaviors attached to this component. | yii\base\Component
getId() | Returns the ID of the widget. | yii\base\Widget
getView() | Returns the view object that can be used to render views or view files. | yii\base\Widget
getViewPath() | Returns the directory containing the view files for this widget. | yii\base\Widget
hasEventHandlers() | Returns a value indicating whether there is any handler attached to the named event. | yii\base\Component
hasMethod() | Returns a value indicating whether a method is defined. | yii\base\Component
hasProperty() | Returns a value indicating whether a property is defined for this component. | yii\base\Component
init() | Initializes the widget. | yii\captcha\Captcha
off() | Detaches an existing event handler from this component. | yii\base\Component
on() | Attaches an event handler to an event. | yii\base\Component
registerClientScript() | Registers the needed JavaScript. | yii\captcha\Captcha
render() | Renders a view. | yii\base\Widget
renderFile() | Renders a view file. | yii\base\Widget
run() | Renders the widget. | yii\captcha\Captcha
setId() | Sets the ID of the widget. | yii\base\Widget
setView() | Sets the view object to be used by this widget. | yii\base\Widget
trigger() | Triggers an event. | yii\base\Component
widget() | Creates a widget instance and runs it. | yii\base\Widget

## Protected Methods

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Method | Description | Defined By
--- | --- | ---
getClientOptions() | Returns the options for the captcha JS widget. | yii\captcha\Captcha
hasModel() |  | yii\widgets\InputWidget
renderInputHtml() | Render a HTML input tag. | yii\widgets\InputWidget

## Events

Hide inherited events

Event | Type | Description | Defined By
--- | --- | --- | ---
EVENT_AFTER_RUN | yii\base\WidgetEvent | An event raised right after executing a widget. (available since version 2.0.11) | yii\base\Widget
EVENT_BEFORE_RUN | yii\base\WidgetEvent | An event raised right before executing a widget. (available since version 2.0.11) | yii\base\Widget
EVENT_INIT | yii\base\Event | An event that is triggered when the widget is initialized via init(). (available since version 2.0.11) | yii\base\Widget

## Property Details

$captchaAction public property

The route of the action that generates the CAPTCHA images. The action represented by this route must be an action of yii\captcha\CaptchaAction. Please refer to yii\helpers\Url::toRoute() for acceptable formats.

public string|array $captchaAction = 'site/captcha'
$imageOptions public property

HTML attributes to be applied to the CAPTCHA image tag.

See also yii\helpers\Html::renderTagAttributes() for details on how attributes are being rendered.

public array $imageOptions = []
$options public property

The HTML attributes for the input tag.

See also yii\helpers\Html::renderTagAttributes() for details on how attributes are being rendered.

public array $options = ['class' => 'form-control']
$template public property

The template for arranging the CAPTCHA image tag and the text input tag. In this template, the token `{image}` will be replaced with the actual image tag, while `{input}` will be replaced with the text input tag.

public string $template = '{image} {input}'

## Method Details

checkRequirements() public static method

Checks if there is graphic extension available to generate CAPTCHA images.

This method will check the existence of ImageMagick and GD extensions.

public static string checkRequirements ( )
return | string | The name of the graphic extension, either "imagick" or "gd".
throws | yii\base\InvalidConfigException | if neither ImageMagick nor GD is installed.

getClientOptions() protected method

Returns the options for the captcha JS widget.

protected array getClientOptions ( )
return | array | The options

init() public method

Initializes the widget.

public void init ( )

registerClientScript() public method

Registers the needed JavaScript.

public void registerClientScript ( )

run() public method

Renders the widget.

public void run ( )