# yii\base

> 38 classes, 6 interfaces, 4 traits of the yii\base namespace.

[API reference](/docs/api/index.md) › [yii](/docs/api/yii/index.md) › base

## Classes

| Class | Summary |
| --- | --- |
| [`Action`](/docs/api/yii/base/action/index.md) | Action is the base class for all controller action classes. |
| [`ActionEvent`](/docs/api/yii/base/actionevent/index.md) | ActionEvent represents the event parameter used for an action event. |
| [`ActionFilter`](/docs/api/yii/base/actionfilter/index.md) | ActionFilter is the base class for action filters. |
| [`Application`](/docs/api/yii/base/application/index.md) abstract | Application is the base class for all application classes. |
| [`BaseObject`](/docs/api/yii/base/baseobject/index.md) | BaseObject is the base class that implements the *property* feature. |
| [`Behavior`](/docs/api/yii/base/behavior/index.md) | Behavior is the base class for all behavior classes. |
| [`Component`](/docs/api/yii/base/component/index.md) | Component is the base class that implements the *property*, *event* and *behavior* features. |
| [`Controller`](/docs/api/yii/base/controller/index.md) | Controller is the base class for classes containing controller logic. |
| [`DynamicModel`](/docs/api/yii/base/dynamicmodel/index.md) | DynamicModel is a model class that supports defining attributes at run-time (the so-called "dynamic attributes") using its constructor or [`defineAttribute()`](/docs/api/yii/base/dynamicmodel/index.md#method-defineAttribute). DynamicModel can be used to support ad hoc data validation. |
| [`ErrorException`](/docs/api/yii/base/errorexception/index.md) | ErrorException represents a PHP error. |
| [`ErrorHandler`](/docs/api/yii/base/errorhandler/index.md) abstract | ErrorHandler handles uncaught PHP errors and exceptions. |
| [`Event`](/docs/api/yii/base/event/index.md) | Event is the base class for all event classes. |
| [`Exception`](/docs/api/yii/base/exception/index.md) | Exception represents a generic exception for all purposes. |
| [`ExitException`](/docs/api/yii/base/exitexception/index.md) | ExitException represents a normal termination of an application. |
| [`InlineAction`](/docs/api/yii/base/inlineaction/index.md) | InlineAction represents an action that is defined as a controller method. |
| [`InvalidArgumentException`](/docs/api/yii/base/invalidargumentexception/index.md) | InvalidArgumentException represents an exception caused by invalid arguments passed to a method. |
| [`InvalidCallException`](/docs/api/yii/base/invalidcallexception/index.md) | InvalidCallException represents an exception caused by calling a method in a wrong way. |
| [`InvalidConfigException`](/docs/api/yii/base/invalidconfigexception/index.md) | InvalidConfigException represents an exception caused by incorrect object configuration. |
| [`InvalidRouteException`](/docs/api/yii/base/invalidrouteexception/index.md) | InvalidRouteException represents an exception caused by an invalid route. |
| [`InvalidValueException`](/docs/api/yii/base/invalidvalueexception/index.md) | InvalidValueException represents an exception caused by a function returning a value of unexpected type. |
| [`Model`](/docs/api/yii/base/model/index.md) | Model is the base class for data models. |
| [`ModelEvent`](/docs/api/yii/base/modelevent/index.md) | ModelEvent represents the parameter needed by [`Model`](/docs/api/yii/base/model/index.md) events. |
| [`Module`](/docs/api/yii/base/module/index.md) | Module is the base class for module and application classes. |
| [`NotSupportedException`](/docs/api/yii/base/notsupportedexception/index.md) | NotSupportedException represents an exception caused by accessing features that are not supported. |
| [`Request`](/docs/api/yii/base/request/index.md) abstract | Request represents a request that is handled by an [`Application`](/docs/api/yii/base/application/index.md). |
| [`Response`](/docs/api/yii/base/response/index.md) | Response represents the response of an [`Application`](/docs/api/yii/base/application/index.md) to a [`Request`](/docs/api/yii/base/request/index.md). |
| [`Security`](/docs/api/yii/base/security/index.md) | Security provides a set of methods to handle common security-related tasks. |
| [`Theme`](/docs/api/yii/base/theme/index.md) | Theme represents an application theme. |
| [`UnknownClassException`](/docs/api/yii/base/unknownclassexception/index.md) | UnknownClassException represents an exception caused by using an unknown class. |
| [`UnknownMethodException`](/docs/api/yii/base/unknownmethodexception/index.md) | UnknownMethodException represents an exception caused by accessing an unknown object method. |
| [`UnknownPropertyException`](/docs/api/yii/base/unknownpropertyexception/index.md) | UnknownPropertyException represents an exception caused by accessing unknown object properties. |
| [`UserException`](/docs/api/yii/base/userexception/index.md) | UserException is the base class for exceptions that are meant to be shown to end users. |
| [`View`](/docs/api/yii/base/view/index.md) | View represents a view object in the MVC pattern. |
| [`ViewEvent`](/docs/api/yii/base/viewevent/index.md) | ViewEvent represents events triggered by the [`View`](/docs/api/yii/base/view/index.md) component. |
| [`ViewNotFoundException`](/docs/api/yii/base/viewnotfoundexception/index.md) | ViewNotFoundException represents an exception caused by view file not found. |
| [`ViewRenderer`](/docs/api/yii/base/viewrenderer/index.md) abstract | ViewRenderer is the base class for view renderer classes. |
| [`Widget`](/docs/api/yii/base/widget/index.md) | Widget is the base class for widgets. |
| [`WidgetEvent`](/docs/api/yii/base/widgetevent/index.md) | WidgetEvent represents the event parameter used for a widget event. |

## Interfaces

| Interface | Summary |
| --- | --- |
| [`Arrayable`](/docs/api/yii/base/arrayable/index.md) | Arrayable is the interface that should be implemented by classes who want to support customizable representation of their instances. |
| [`BootstrapInterface`](/docs/api/yii/base/bootstrapinterface/index.md) | BootstrapInterface is the interface that should be implemented by classes who want to participate in the application bootstrap process. |
| [`Configurable`](/docs/api/yii/base/configurable/index.md) | Configurable is the interface that should be implemented by classes who support configuring its properties through the last parameter to its constructor. |
| [`DynamicContentAwareInterface`](/docs/api/yii/base/dynamiccontentawareinterface/index.md) | DynamicContentAwareInterface is the interface that should be implemented by classes which support a [`View`](/docs/api/yii/base/view/index.md) dynamic content feature. |
| [`StaticInstanceInterface`](/docs/api/yii/base/staticinstanceinterface/index.md) | StaticInstanceInterface is the interface for providing static instances to classes, which can be used to obtain class meta information that can not be expressed in static methods. |
| [`ViewContextInterface`](/docs/api/yii/base/viewcontextinterface/index.md) | ViewContextInterface is the interface that should implemented by classes who want to support relative view names. |

## Traits

| Trait | Summary |
| --- | --- |
| [`ArrayableTrait`](/docs/api/yii/base/arrayabletrait/index.md) | ArrayableTrait provides a common implementation of the [`Arrayable`](/docs/api/yii/base/arrayable/index.md) interface. |
| [`ArrayAccessTrait`](/docs/api/yii/base/arrayaccesstrait/index.md) | ArrayAccessTrait provides the implementation for [`IteratorAggregate`](https://www.php.net/manual/en/class.iteratoraggregate.php), [`ArrayAccess`](https://www.php.net/manual/en/class.arrayaccess.php) and [`Countable`](https://www.php.net/manual/en/class.countable.php). |
| [`DynamicContentAwareTrait`](/docs/api/yii/base/dynamiccontentawaretrait/index.md) | DynamicContentAwareTrait implements common methods for classes which support a [`View`](/docs/api/yii/base/view/index.md) dynamic content feature. |
| [`StaticInstanceTrait`](/docs/api/yii/base/staticinstancetrait/index.md) | StaticInstanceTrait provides methods to satisfy [`StaticInstanceInterface`](/docs/api/yii/base/staticinstanceinterface/index.md) interface. |