--- title: "Developing a custom ViewHelper" manual: "TYPO3 Explained" version: "13.4" permalink: "https://docs.typo3.org/permalink/t3coreapi:fluid-custom-viewhelper@13.4" source: "ApiOverview/Fluid/DevelopCustomViewhelper.rst" rendered: "2026-09-28T12:45:33+00:00" --- # Developing a custom ViewHelper {#fluid-custom-viewhelper} The traits \TYPO3Fluid\Fluid\Core\ViewHelper\Traits\CompileWithRenderStatic and \TYPO3Fluid\Fluid\Core\ViewHelper\Traits\CompileWithContentArgumentAndRender are deprecated. See section migration. This chapter demonstrates how to write a custom Fluid ViewHelper in TYPO3. A "Gravatar" ViewHelper is created, which uses an email address as parameter and shows the picture from gravatar.com if it exists. The official documentation of Fluid for writing custom ViewHelpers can be found within the Fluid documentation: [Creating ViewHelpers](https://docs.typo3.org/other/typo3fluid/fluid/main/en-us/Extending/ViewHelpers.html#creating-viewhelpers). **Contents of this page** - [Fluid](https://docs.typo3.org/permalink/t3coreapi:fluid@13.4) - [AbstractViewHelper implementation](https://docs.typo3.org/permalink/t3coreapi:abstractviewhelper-implementation@13.4) - [Creating HTML/XML tags with the AbstractTagBasedViewHelper](https://docs.typo3.org/permalink/t3coreapi:creating-html-xml-tags-with-the-php-abstracttagbasedviewhelper@13.4) - [Insert optional arguments with default values](https://docs.typo3.org/permalink/t3coreapi:insert-optional-arguments-with-default-values@13.4) - [Prepare ViewHelper for inline syntax](https://docs.typo3.org/permalink/t3coreapi:prepare-viewhelper-for-inline-syntax-1@13.4) - [Handle additional arguments](https://docs.typo3.org/permalink/t3coreapi:handle-additional-arguments-1@13.4) - [The different render methods](https://docs.typo3.org/permalink/t3coreapi:the-different-render-methods-1@13.4) - [Migration: Remove deprecated compliling traits](https://docs.typo3.org/permalink/t3coreapi:migration-remove-deprecated-compliling-traits@13.4) - [How to access objects in the ViewHelper implementation](https://docs.typo3.org/permalink/t3coreapi:how-to-access-objects-in-the-viewhelper-implementation@13.4) ## Fluid {#fluid-custom-viewhelper-fluid} The custom ViewHelper is not part of the default distribution. Therefore a namespace import is necessary to use this ViewHelper. In the following example, the namespace `\MyVendor\MyExtension\ViewHelpers` is imported with the prefix `m`. Now, all tags starting with `m:` are interpreted as ViewHelper from within this namespace. For further information about namespace import, see [Fluid](https://docs.typo3.org/permalink/t3coreapi:fluid-syntax-viewhelpers-import-namespaces@13.4). The ViewHelper should be given the name "gravatar" and take an email address and an optional alt-text as a parameters. The ViewHelper is called in the template as follows: **EXT:my_extension/Resources/Private/Templates/SomeTemplate.html** ```html ``` ## AbstractViewHelper implementation {#fluid-custom-viewhelper-implementation} Every ViewHelper is a PHP class. For the Gravatar ViewHelper, the fully qualified name of the class is `\MyVendor\MyExtension\ViewHelpers\GravatarViewHelper`. **Example 1: EXT:my_extension/Classes/ViewHelpers/GravatarViewHelper.php** ```php registerArgument( 'emailAddress', 'string', 'The email address to resolve the gravatar for', true, ); $this->registerArgument( 'alt', 'string', 'The optional alt text for the image', ); } public function render(): string { $emailAddress = $this->arguments['emailAddress']; $altText = $this->arguments['alt'] ?? ''; // this is improved with the TagBasedViewHelper (see below) return sprintf( '%s', md5($emailAddress), htmlspecialchars($altText), ); } } ``` ### `AbstractViewHelper` {#fluid-custom-viewhelper-abstractviewhelper} *line 9* `extends AbstractViewHelper` Every ViewHelper must inherit from the class `\TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper`. A ViewHelper can also inherit from subclasses of `\TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper`, for example from `\TYPO3Fluid\Fluid\Core\ViewHelper\AbstractTagBasedViewHelper`. Several subclasses are offering additional functionality. The `\TYPO3Fluid\Fluid\Core\ViewHelper\AbstractTagBasedViewHelper` will be explained [later on in this chapter](https://docs.typo3.org/permalink/t3coreapi:creating-xml-tags-using-tagbasedviewhelper@13.4) in detail. ### Disable escaping the output {#fluid-viewhelper-custom-escaping-of-output} *line 11* `protected $escapeOutput = false;` By default, all output is escaped by `htmlspecialchars()` to prevent cross site scripting. Setting the property `$escapeOutput` to false is necessary to prevent escaping of ViewHelper output. By setting the property `$escapeChildren` to false, escaping of the tag content (its child nodes) can be disabled. If this is not set explicitly, the value will be determined automatically: If `$escapeOutput`: is true, `$escapeChildren` will be disabled to prevent double escaping. If `$escapeOutput`: is false, `$escapeChildren` will be enabled unless disabled explicitly. Passing in children is explained in [Prepare ViewHelper for inline syntax](https://docs.typo3.org/permalink/t3coreapi:prepare-viewhelper-for-inline-syntax@13.4). ### `initializeArguments()` {#fluid-viewhelper-custom-initializearguments} *line 13* `public function initializeArguments(): void` The `Gravatar` ViewHelper must hand over the email address which identifies the Gravatar. An alt text for the image is passed as optional parameter. ViewHelpers have to register (line 16, `$this->registerArgument()`) parameters. The registration happens inside method `initializeArguments()`. In the example above, the ViewHelper receives the argument `emailAddress` (line 17) of type `string` (line 18) which is mandatory (line 19). The optional argument `alt` is defined in lines 22-26. These arguments can be accessed through the array `$this->arguments`, in method `render()`. > [!TIP] > Sometimes arguments can take various types. In this case, the type `mixed` > should be used. ### `render()` {#fluid-custom-viewhelper-implementation-render} *line 29* `public function render(): string` The method `render()` is called once the ViewHelper is rendered. Its return value can be directly output in Fluid or passed to another ViewHelper. In *line 30 an 31* we retrieve the arguments from the `$arguments` class property. `alt` is an optional argument and therefore nullable. Fluid ensures, the declared type is passed for non-null values. These arguments can contain user input. > [!WARNING] > **Attention** > > Prevent [XSS (Cross-Site Scripting) attacks](https://docs.typo3.org/permalink/t3coreapi:prevent-cross-site-scripting@13.4). > > The returned string is displayed raw, without being passed through > `htmlspecialchars()` as we have > [disabled escaping](https://docs.typo3.org/permalink/t3coreapi:fluid-viewhelper-custom-escaping-of-output@13.4). If escaping is disabled, the `render()` method is responsible for preventing [XSS attacks](https://docs.typo3.org/permalink/t3coreapi:prevent-cross-site-scripting@13.4). Therefore all arguments **must** be sanitized before they are returned. Passing the email address through [md5()](https://www.php.net/manual/en/function.md5.php) ensures that we only have a hexadecimal number, it can contain no harmful chars. The alt text is passed through `htmlspecialchars()`, therefore potentially harmful chars are escaped. > [!TIP] > **Hint** > > The `render()` method usually returns a string that should be displayed > directly in the Fluid template. But it is also possible to return another > type and use it as argument for another ViewHelper which expects that type. ## Creating HTML/XML tags with the `AbstractTagBasedViewHelper` {#creating-html-tags-using-tagbasedviewhelper} All TagBasedViewHelpers (such as or ) can now receive arbitrary tag attributes which will be appended to the resulting HTML tag. In the past, this was only possible for a small list of tag attributes, like class, id or lang.See also Migration: Remove registerUniversalTagAttributes and registerTagAttribute. For ViewHelpers which create HTML/XML tags, Fluid provides an enhanced base class: `\TYPO3Fluid\Fluid\Core\ViewHelper\AbstractTagBasedViewHelper`. This base class provides an instance of `\TYPO3Fluid\Fluid\Core\ViewHelper\TagBuilder` that can be used to create HTML-tags. It takes care of the syntactically correct creation and, for example, escapes single and double quotes in attribute values. *line 11* `protected $tagName = 'img'` configures the name of the HTML/XML tag to be output. All ViewHelpers extending `\TYPO3Fluid\Fluid\Core\ViewHelper\AbstractTagBasedViewHelper` can receive arbitrary tag attributes which will be appended to the resulting HTML tag and escaped automatically. For example we do not have to declare or escape the `alt` argument as we did in [Example 1](https://docs.typo3.org/permalink/t3coreapi:fluid-custom-viewhelper-implementation@13.4). Because the Gravatar ViewHelper creates an `` tag the use of the `\TYPO3Fluid\Fluid\Core\ViewHelper\TagBuilder`, stored in class property `$this->tag` is advised: **EXT:my_extension/Classes/ViewHelpers/GravatarViewHelper.php (Example 2, tag-based)** ```php registerArgument( 'emailAddress', 'string', 'The email address to resolve the gravatar for', true, ); // The alt argument will be automatically registered } public function render(): string { $emailAddress = $this->arguments['emailAddress']; $this->tag->addAttribute( 'src', 'https://www.gravatar.com/avatar/' . md5($emailAddress), ); return $this->tag->render(); } } ``` *line 32* `$this->tag->render()` creates the `` tag with all explicitly added arguments (*line 28-31* `$this->tag->addAttribute()`) and all arbitrary tag attributes passed to the ViewHelper when it is used. ### `AbstractTagBasedViewHelper` {#abstracttagbasedviewhelper} *line 6* `class GravatarViewHelper extends AbstractTagBasedViewHelper` The ViewHelper does not inherit directly from `\TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper` but from `\TYPO3Fluid\Fluid\Core\ViewHelper\AbstractTagBasedViewHelper`, which provides and initializes the `\TYPO3Fluid\Fluid\Core\ViewHelper\TagBuilder` and passes on and escapes arbitrary tag attributes. ### `$tagName` {#abstracttagbasedviewhelper-tagname} *line 9* `protected $tagName = 'img';` There is a class property `$tagName` which stores the name of the tag to be created (``). ### `$this->tag->addAttribute()` {#abstracttagbasedviewhelper-addattribute} *line 28 - 31* `$this->tag->addAttribute(...)` The tag builder is available as class property `$this->tag`. It offers the method `TagBuilder::addAttribute()` to add new tag attributes. In our example the attribute `src` is added to the tag. ### `$this->tag->render()` {#abstracttagbasedviewhelper-render} *line 32* `return $this->tag->render();` The GravatarViewHelper creates an img tag builder, which has a method named `render()`. After configuring the tag builder instance, the rendered tag markup is returned. ### `$this->registerTagAttribute()` {#abstracttagbasedviewhelper-registertagattribute} The methods php:$this->registerTagAttribute() and registerUniversalTagAttributes() have been deprecated. They can be removed on dropping TYPO3 v12.4 support. #### Migration: Remove registerUniversalTagAttributes and registerTagAttribute {#abstracttagbasedviewhelper-registertagattribute-migration} **EXT:my_extension/Classes/ViewHelpers/GravatarViewHelper.php** ```diff public function initializeArguments(): void { parent::initializeArguments(); + $this->registerUniversalTagAttributes(); + $this->registerTagAttribute('alt', 'string', 'Alternative Text for the image'); } ``` When removing the call, attributes registered by the call are now available in `$this->additionalArguments`, and no longer in `$this->arguments`. This *may* need adaption within single ViewHelpers, *if* they handle such attributes on their own. If you need to support both TYPO3 v12.4 and v13, you can leave the calls in until dropping TYPO3 v12.4 support. **EXT:my_extension/Classes/ViewHelpers/GravatarViewHelper.php** ```diff public function initializeArguments(): void { parent::initializeArguments(); + // TODO: Remove registerUniversalTagAttributes and registerTagAttribute + // On dropping TYPO3 v12.4 support. $this->registerUniversalTagAttributes(); $this->registerTagAttribute('alt', 'string', 'Alternative Text for the image'); } ``` ## Insert optional arguments with default values {#insert-optional-arguments} An optional size for the image can be provided to the Gravatar ViewHelper. This size parameter will determine the height and width in pixels of the image and can range from 1 to 512. When no size is given, an image of 80px is generated. The `render()` method can be improved like this: **EXT:my_extension/Classes/ViewHelpers/GravatarViewHelper.php** ```php registerArgument( 'emailAddress', 'string', 'The email address to resolve the gravatar for', true, ); $this->registerArgument( 'size', 'integer', 'The size of the gravatar, ranging from 1 to 512', false, 80, ); } public function render(): string { $emailAddress = $this->arguments['emailAddress']; $size = $this->arguments['size']; $this->tag->addAttribute( 'src', sprintf( 'http://www.gravatar.com/avatar/%s?s=%s', md5($emailAddress), urlencode($size), ), ); return $this->tag->render(); } } ``` With this setting of a default value and setting the fourth argument to `false`, the `size` attribute becomes optional. ## Prepare ViewHelper for inline syntax {#prepare-viewhelper-for-inline-syntax} In former versions this was done by using the now deprecated trait CompileWithContentArgumentAndRender. See section migration. So far, the Gravatar ViewHelper has focused on the tag structure of the ViewHelper. The call to render the ViewHelper was written with tag syntax, which seemed obvious because it itself returns a tag: **EXT:my_extension/Resources/Private/Templates/SomeTemplate.html** ```html ``` Alternatively, this expression can be written using the inline notation: **EXT:my_extension/Resources/Private/Templates/SomeTemplate.html** ```html {m:gravatar(emailAddress: post.author.emailAddress)} ``` One should see the Gravatar ViewHelper as a kind of post-processor for an email address and would allow the following syntax: **EXT:my_extension/Resources/Private/Templates/SomeTemplate.html** ```html {post.author.emailAddress -> m:gravatar()} ``` This syntax places focus on the variable that is passed to the ViewHelper as it comes first. The syntax `{post.author.emailAddress -> m:gravatar()}` is an alternative syntax for `{post.author.emailAddress}`. To support this, the email address comes either from the argument `emailAddress` or, if it is empty, the content of the tag should be interpreted as email address. This is typically used with formatting ViewHelpers. These ViewHelpers all support both tag mode and inline syntax. Depending on the implemented method for rendering, the implementation is different: To fetch the content of the ViewHelper the method `renderChildren()` is available in the `\TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper`. This returns the evaluated object between the opening and closing tag. **EXT:my_extension/Classes/ViewHelpers/GravatarViewHelper.php (Example 3, with content arguments)** ```php registerArgument( 'emailAddress', 'string', 'The email address to resolve the gravatar for', // The argument is optional now ); } public function render(): string { $emailAddress = $this->renderChildren(); // The children of the ViewHelper might be empty now if ($emailAddress === null) { throw new \Exception( 'The Gravatar ViewHelper expects either the ' . 'argument "emailAddress" or the content to be set. ', 1726035545, ); } // Or someone could pass a non-string value if (!is_string($emailAddress) || !filter_var($emailAddress, FILTER_VALIDATE_EMAIL)) { throw new \Exception( 'The Gravatar ViewHelper expects a valid ' . 'e-mail address as input. ', 1726035546, ); } $this->tag->addAttribute( 'src', 'https://www.gravatar.com/avatar/' . md5($emailAddress), ); return $this->tag->render(); } public function getContentArgumentName(): string { return 'emailAddress'; } } ``` ## Handle additional arguments {#handle-additional-arguments} All ViewHelpers implementing AbstractTagBasedViewHelper can now receive arbitrary tag attributes which will be appended to the resulting HTML tag. In the past, this was only possible for explicitly registered arguments.See also Migration: Remove registerUniversalTagAttributes and registerTagAttribute. If a ViewHelper allows further arguments which have not been explicitly configured, the `handleAdditionalArguments()` method can be implemented. ViewHelper implementing `\TYPO3Fluid\Fluid\Core\ViewHelper\AbstractTagBasedViewHelper` do not need to use this as all arguments are passed on automatically. ## The different render methods {#the-different-render-methods} ViewHelpers can have one or more of the following methods for implementing the rendering. The following section will describe the differences between the implementations. ### `render()` method {#render-method} This method is usually implemented. ### `compile()`-Method {#compile-method} This method can be overwritten to define how the ViewHelper should be compiled. That can make sense if the ViewHelper itself is a wrapper for another native PHP function or TYPO3 function. In that case, the method can return the call to this function and remove the need to call the ViewHelper as a wrapper at all. The `compile()` has to return the compiled PHP code for the ViewHelper. Also the argument `$initializationPhpCode` can be used to add further PHP code before the execution. Example implementation: **EXT:my_extension/Classes/ViewHelpers/StrtolowerViewHelper.php** ```php registerArgument('string', 'string', 'The string to lowercase.', true); } public function compile( $argumentsName, $closureName, &$initializationPhpCode, ViewHelperNode $node, TemplateCompiler $compiler, ): string { return sprintf("strtolower(%s['string'])", $argumentsName); } } ``` ### `renderStatic()` method {#renderstatic-method} The trait CompileWithRenderStatic, which is responsible for calling renderStatic() is deprecated. See section migration. ### `render()` method {#render-method} Most of the time, this method is implemented. ## Migration: Remove deprecated compliling traits {#fluid-custom-viewhelper-migration} ### Migration: Remove deprecated trait `CompileWithRenderStatic` {#fluid-viewhelper-custom-renderstatic} To remove the deprecated trait `\TYPO3Fluid\Fluid\Core\ViewHelper\Traits\CompileWithRenderStatic` switch to use the `render()` method instead of the `renderStatic()`. **EXT:my_extension/Classes/ViewHelpers/GravatarViewHelper.php (diff removing CompileWithRenderStatic)** ```diff registerArgument('emailAddress', 'string', 'The email address to resolve the gravatar for', true); } - public static function renderStatic(array $arguments, \Closure $renderChildrenClosure, RenderingContextInterface $renderingContext): string { + public function render(): string { - $emailAddress = $arguments['emailAddress']; + $emailAddress = $this->arguments['emailAddress']; return sprintf('', md5($emailAddress)); } } ``` - ***line 13*** Remove the trait `\TYPO3Fluid\Fluid\Core\ViewHelper\Traits\CompileWithRenderStatic`. - ***lines 23, 24*** Switch the render method from `renderStatic()` to `render()`. - ***lines 25, 26*** Fetch the arguments from the class property instead method argument. ### Migration: Remove deprecated trait `CompileWithContentArgumentAndRenderStatic` {#fluid-custom-viewhelper-compilewithcontentargumentandrenderstatic-migration} If `\TYPO3Fluid\Fluid\Core\ViewHelper\Traits\CompileWithContentArgumentAndRender` was also used in your ViewHelper implementation, further steps are needed: **EXT:my_extension/Classes/ViewHelpers/GravatarViewHelper.php (diff removing CompileWithContentArgumentAndRender)** ```diff registerArgument('emailAddress', 'string', 'The email address to resolve the gravatar for'); } - public static function renderStatic(array $arguments, \Closure $renderChildrenClosure, RenderingContextInterface $renderingContext): string { + public function render(): string { - $emailAddress = $renderChildrenClosure(); + $emailAddress = $this->renderChildren(); return sprintf('', md5($emailAddress)); } public function getContentArgumentName(): string { return 'emailAddress'; } } ``` - ***line 13*** Remove the trait `\TYPO3Fluid\Fluid\Core\ViewHelper\Traits\CompileWithContentArgumentAndRender`. - ***lines 22, 23*** Switch the render method from `renderStatic()` to `render()`. - ***lines 24, 25*** Use the non-static method `$this->renderChildren()` instead of the closure `$renderChildrenClosure()`. ### Remove calls to removed `renderStatic()` method of another ViewHelper {#remove-calls-to-removed-renderstatic-method-of-another-viewhelper} If you called a now removed `renderStatic()` method from within another ViewHelper's `renderStatic()` method you can replace the code like this: **EXT:my_extension/Classes/ViewHelpers/GravatarViewHelper.php (diff replacing renderStatic() calls)** ```diff registerArgument('emailAddress', 'string', 'The email address to resolve the gravatar for', true); } - public static function renderStatic(array $arguments, \Closure $renderChildrenClosure, RenderingContextInterface $renderingContext): string + public function render(): string { - $emailAddress = $arguments['emailAddress']; + $emailAddress = $this->arguments['emailAddress']; - $gravatorUrl = GravatarUrlViewHelper::renderStatic(['email', $emailAddress], $renderChildrenClosure, $renderingContext); + $gravatarUrl = $this->renderingContext->getViewHelperInvoker()->invoke( + GravatarUrlViewHelper::class, + ['email', $emailAddress], + $this->renderingContext, + $this->renderChildren(), + ); return sprintf('', $gravatarUrl); } } ``` - ***line 27, 28ff*** Replace the static call to the `renderStatic()` method of another ViewHelper by calling `$this->renderingContext->getViewHelperInvoker()->invoke()` instead. See also `\TYPO3Fluid\Fluid\Core\ViewHelper\ViewHelperInvoker`. ## How to access objects in the ViewHelper implementation {#fluid-custom-viewhelper-access} Custom ViewHelper implementations support [Dependency injection](https://docs.typo3.org/permalink/t3coreapi:dependency-injection@13.4). You can, for example, inject the `\TYPO3\CMS\Core\Configuration\ExtensionConfiguration` service to get the configuration of an installed extension. Note that ViewHelpers should avoid getting additional data from the database because this violates the separation of data (model) and presentation (view). Some objects depend on the current context and can be fetched from the rendering context: ### Accessing the current Request in a ViewHelper implementation {#fluid-custom-viewhelper-access-request} The current `\Psr\Http\Message\ServerRequestInterface` object can be fetched from the `\TYPO3\CMS\Fluid\Core\Rendering\RenderingContext` inside the `render()` method in a ViewHelper implementation,: **EXT:my_extension/Classes/ViewHelpers/SomeViewHelper.php** ```php use Psr\Http\Message\ServerRequestInterface; public function render(): string { if ($this->renderingContext->hasAttribute(ServerRequestInterface::class)) { $request = $this->renderingContext->getAttribute(ServerRequestInterface::class); } return 'Hello World!'; } ``` Note that the request may not be available in all Fluid template contexts, so use `hasAttribute()` first to check if it exists. The request may contain other attributes that are relevant for your ViewHelper's use case. See [TYPO3 request attributes](https://docs.typo3.org/permalink/t3coreapi:request-attributes@13.4) for a list of available attributes. ### Using stdWrap / fetching the current ContentObject in a ViewHelper implementation {#fluid-custom-viewhelper-access-contentobject} You can [access the ContentObjectRenderer](https://docs.typo3.org/permalink/t3coreapi:tsfe-contentobjectrenderer@13.4) from the `\Psr\Http\Message\ServerRequestInterface`: **EXT:my_extension/Classes/ViewHelpers/SomeViewHelper.php** ```php use TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer; public function render(): string { if ($this->renderingContext->hasAttribute(ServerRequestInterface::class)) { $request = $this->renderingContext->getAttribute(ServerRequestInterface::class); $cObj = $request->getAttribute('currentContentObject'); return $cObj->stdWrap('Hello World', ['wrap' => '|!']); } return ''; } ``` The class TypoScriptFrontendController and its global instance $GLOBALS['TSFE'], which were formerly used to fetch the ContentObjectRenderer, have been marked as deprecated. The class will be removed in TYPO3 v14. See TSFE for migration steps.