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API to declare parameters for any Fluid template/section

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1.4.0 2023-03-17 15:01 UTC

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TYPO3 Fluid extension fluid_parameters

API to enable declaring parameters for a Fluid template, partial, layout or section within any of those types of files.

What does it do?

In short: allows you to declare required and optional parameters for a Fluid asset. It does this by emulating a subset of the features that would have been part of Fluid 3.0, namely f:parameter. On top of this it adds a couple of tricks for convenience.


To install, simply do composer req namelesscoder/fluid-parameters. That's it - no configuration is necessary. If you use the package in a TYPO3 CMS installation this automatically adds f:parameter, f:description and f:parameter.mode as ViewHelpers. If you are not within a TYPO3 CMS installation you nave to manually add the namespace {namespace f=\NamelessCoder\FluidParameters\ViewHelpers} in templates where you want to use the feature.

Feature set:

  • Parameters can be declared for any Fluid asset; Templates, Layouts, Partials or Sections (within any of those three types of Fluid assets).
  • Parameters can be required, in which case an error is thrown if the required variable is not assigned as template variable or passed to the section/partial with arguments on f:render.
  • Parameters can be optional, in which case if they are not passed, they can be given a default value (precisely like a ViewHelper argument) and become assigned when rendering the asset.
  • Parameters can be cast to the appropriate type like string or integer.
  • Parameters can be given a list of allowed values. If you declare a parameter which allows for example values "foo" or "bar" but the variable value is "baz" when you render the asset, an error can be thrown.
  • Specifying a parameter with type array allows you to pass a CSV value as variable, to make it easier to pass array values as part of arguments on f:render without complex Fluid syntax - or directly consume values from records without exploding CSV values stored in the record's columns.
  • References can be rendered, describing parameters for a given Fluid asset or section.
  • Templates or sections can be provided with a description that can be rendered as part of the parameter reference.

Together, these features allow a developer who writes Fluid template files to ensure that necessary variables are present when the template file is rendered and that optional variables can have a default value. And they allow an integrator who renders the templates to be informed if a necessary variable is not present or does not have a compatible data type - without having detailed knowledge of every template file's content.

How to use:

No configuration is required - simply use the f:parameter ViewHelper in your Fluid template and the rest happens automatically. The f:parameter ViewHelper can be used in any Layout, Template or Partial, and within sections defined in any of those types of files. Declared parameters are specific to the file or section - as soon as you render another file or section, only the parameters of that other file or section will be considered.

Adding a required parameter

<f:parameter name="title" type="string" required="1" />

This throws an error if {title} is not assigned as template variable when rendering the template.

Optional parameter

<f:parameter name="title" type="string" default="Default title" />

This does not throw an error if {title} is not assigned. Instead, it automatically assigns the variable with a value of Default title.

Supported parameter types

  • int, integer
  • string
  • float, double, decimal
  • bool, boolean
  • array
  • DateTime (natively converts UNIXTIME timestamps and date strings to DateTime)
  • object (generic object, cast to stdClass from array)

Furthermore, custom class names are supported and can be specified by FQN or short name. If specified by short name, any object instance of a class with that short name will be allowed - and no type casting will be done. If specified by FQN, only instances of the class or subclasses thereof will be allowed - and type casting will be possible by taking non-object values and passing them as single constructor argument for the class using new $className($value).

Every type, including custom objects, also supports an "array-of-types" by adding [] to the type, e.g. string[]. This can even be done to multiple levels, e.g. string[][] to require "an array of arrays of strings".

Specific required value

<f:parameter name="color" type="string" oneOf="red,green,blue" default="red" />
<span class="color-{color]">Some text that's either red, green or blue</span>

This causes an error to be thrown if assigning variable {color} is not one of the exact values red, green or blue - and selects red as the default value.

Undeclared variables

<f:parameter name="title" type="string" required="1" />

Sets the parameter handling mode to strict which means that if this template is rendered with an undeclared variable, an error is thrown:

<f:render partial="StrictRequirementsPartial" arguments="{title: 'My title', unknownvariable: 'Some value'}" />

Results in an error:

Unxpected (undefined) template variable(s) encountered: unknownvariable

By default, undeclared variables are allowed. By setting the mode to strict this behavior is changed.

Note that f:parameter.mode must be used BEFORE any occurrences of f:parameter to have an effect.

Usage within sections

<f:section name="MySection">
  <f:parameter name="title" type="string" required="1" />
  <f:parameter name="text" type="string" default="Default text" />

Has the exact same effect as declaring the parameter on a template, partial or layout - but only applies when rendering the section. If the section is rendered with an undeclared variable assigned, an error is thrown (due to mode=strict). If {text} is not assigned when rendering the section, it is automatically assigned with a value of Default text.

Describing a template

  This is a description of the template file.
  You must always assign the "title" variable when rendering this template. 
<f:parameter name="title" type="string" required="1" />


<h3>Value of title variable</h3>

Essentially, any content you use within f:description is not rendered as output when the template/section is rendered. Note: do not use any Fluid code within the description block! If you do, the description text will be truncated and only includes any text leading up to the first Fluid code. Invalid Fluid code within this block will still cause a template parsing error!

Extracting "Reflections" of parameters/descriptions

The package contains an API to extract information about which parameters apply to a given template, along with the contents of the f:description block within the template. This can be used to build your own style guide or reference.

Consider the following example template file located at /path/to/my/template.html:

  Text from the description block in my template
<f:parameter name="title" type="string" description="A text to become the title" />
<f:parameter name="text" type="string" description="A text to become the paragraph body" required="1" />
<f:parameter name="level" type="integer" description="Optional header level 1-9" oneOf="1,2,3,4,5,6,7,8,9" />

<f:if condition="{title]">

<f:section name="MySection">
        Text from the description block in section "MySection" in my template
    <f:parameter name="content" type="string" description="Content string to render in the section" required="1" />
    Additional content: {content}

Using the extraction API is fairly straight-forward:

$templateFile = '/path/to/my/template.html';
$renderingContext = new \TYPO3Fluid\Fluid\Core\Rendering\RenderingContext();
$extractor = new \NamelessCoder\FluidParameters\Reflection\ParameterExtractor($renderingContext);
$reflection = $extractor->parseTemplate($templateFile);

The $reflection variable now contains an instance of TemplateReflection which holds properties describing the template. You can use this reflection instance to extract all metadata:

function renderParameterDefinitions(array $parameterDefinitions): array
    $output = [];
    foreach ($parameterDefinitions as $name => $definition) {
        $output[] = '  Parameter: ' . $name;
        $output[] = '  Description: ' . $definition->getDescription();
        $output[] = '  Required: ' . ($definition->isRequired() ? 'Yes' : 'No');
        $output[] = '  Type: ' . $definition->getType();
        if (!$definition->isRequired()) {
            $output[] = '  Default: ' . var_export($definition->getDefaultValue(), true);        
        if (!empty($definition->getOneOf())) {
            $output[] = '  Allowed values: ' . implode(', ', $definition->getOneOf());        
        $output[] = PHP_EOL;
    return $output;

$description = $reflection->getDescription();
$parameterMode = $reflection->getParameterMode();

$output = [
    'Template: ' . $templateFile,
    'Parameter mode: ' . $parameterMode,
    '  ' . $description,

$output = array_merge($output, renderParameterDefinitions($reflection->getParameterDefinitions()));

It is further possible to extract the same type of reference for each of the f:section nodes within the template file. Each of the values returned from $reflection->getSections() is an instance of SectionReflection:

// You can extract a single known section and chain getters:
$mySectionDescription = $reflection->fetchSection('MySection')->getDescription();

// Or iterate over all sections within the template:
foreach ($reflection->getSections() as $sectionName => $sectionReflection) {
    $output[] = 'Template: ' . $templateFile . ', section: ' . $sectionName;
    $output[] = 'Parameter mode: ' . $parameterMode;
    $output[] = 'Description:';
    $output[] = $description;
    $output[] = 'Parameters:';
    $output = array_merge($output, renderParaterDefinitions($sectionReflection->getParameterDefinitions()));
    $output[] = PHP_EOL;

echo implode(PHP_EOL, $output);

Together this would produce an output like this:

Template: /path/to/my/template.html
Parameter mode: strict
  Text from the description block in my template
  Parameter: title
  Description: A text to become the title
  Required: No
  Type: string
  Default: null
  Parameter: text
  Description: A text to become the paragraph body
  Required: Yes
  Type: string
  Parameter: level
  Description: Optional header level 1-9
  Required: No
  Type: integer
  Default: 1
  Allowed values: 1, 2, 3, 4, 5, 6, 7, 8, 9 

Template: /path/to/my/template.html, section: MySection
Parameter mode: loose
  Text from the description block in section "MySection" in my template
  Parameter: content
  Description: Content string to render in the section
  Required: Yes
  Type: string

The $reflection instance can of course also be assigned to a Fluid template to render the reference. Use Fluid's standard iteration and variable access to achieve the exact output you want, e.g. {reflection.description}, <f:for each="{reflection.parameterDefinitions}" as="definition">...</f:for> and so on - just like you would normally iterate arrays and output variables.

Differences between this extension and fluid_components

You may or may not already be aware of an extension "Fluid Components" created by sitegeist - these two extensions are somewhat similar in that they allow Fluid templates to define required variables, but they are very different in their implementation philosophy.

These two extensions can coexist peacefully and can be mixed to some extent (sections rendered by Fluid Components can be fitted with parameters declared by Fluid Parameters); however, parameters declared with one are not known to the other. It is therefore a fully viable use case to use Fluid Components for some contexts and Fluid Parameters for others, in the same project.

The following table shows the differences:

Fluid Parameters Fluid Components
Supports declaring parameters for templates
Supports default values for parameters/variables
Supports validation of parameters' data type
Supports reference / parameter documentation
High performance / light-weight
Works for any template
Works for individual sections
Can be rendered as native FLUIDTEMPLATE TS object
Compatible with Flux templates
Works for Fluid outside of TYPO3 CMS *
Requires special syntax to define rendering
Supports custom data type casting
Works by overriding internal Fluid classes
Makes template files emulate a ViewHelper
Requires custom Fluid namespaces
Allows XSD integration for auto-completion
Has a "living styleguide" implementation

(* If you manually register the namespace with {namespace f=\NamelessCoder\FluidParameters\ViewHelpers})

In essence: use Fluid Parameters if you...

  • Only need the ability to declare optional/required parameters and provide default values.
  • Want the smallest possible integration that works without any overrides of internal Fluid classes.
  • Do not want to write additional configuration.
  • Don't care about XSD integration for auto-completion.
  • Still want to use your templates as controller action templates or template file for a FLUIDTEMPLATE TS object.
  • Want to use your template files as content element or page templates with required variables.
  • Want to use the feature in Flux-based templates
  • Want to use the feature in non-TYPO3-CMS projects that use Fluid

And use Fluid Components if you...

  • Don't mind having to write additional configuration.
  • Don't mind that internal Fluid classes are overridden with less performant replacements.
  • Don't care that your affected templates cannot be rendered normally anymore.
  • Need/want XSD integration for auto-completion purposes.
  • Need/want a "living styleguide" (without needing to write the implementation yourself).


This work was kindly sponsored by Busy Noggin.