Symfony expression language

Symfony expression language is used by TYPO3 in certain places. These are documented in the following sections, together with explanations how they can be extended:

Symfony within TypoScript conditions

In order to provide custom conditions, its essential to understand how conditions are written. Refer to The syntax of conditions for details.

Conditions are evaluated by the Symfony Expression Language and are evaluated to boolean results. Therefore an integrator can write [true === true] which would evaluate to true. In order to provide further functionality within conditions, the Symfony Expression Language needs to be extended. There are two parts that can be added to the language, which are variables and functions.

The following sections explain how to add variables and functions.

Registering new provider within an extension

There has to be a provider, no matter whether variables or functions will be provided.

The provider is registered in the extension file /Configuration/ExpressionLanguage.php, depending on the extension’s custom PHP class name:

<?php

return [
    'typoscript' => [
        \Vendor\ExtensionName\ExpressionLanguage\CustomTypoScriptConditionProvider::class,
    ]
];

This will register the defined CustomTypoScriptConditionProvider PHP class as provider within the context typoscript.

Implement provider within extension

The provider itself is written as PHP Class within the extension file /Classes/ExpressionLanguage/CustomTypoScriptConditionProvider.php, depending on the formerly registered PHP class name:

<?php

namespace Vendor\ExtensionName\ExpressionLanguage;

use TYPO3\CMS\Core\ExpressionLanguage\AbstractProvider;

class CustomTypoScriptConditionProvider extends AbstractProvider
{
    public function __construct()
    {
    }
}

Additional variables

Additional variables can already be provided within the CustomTypoScriptConditionProvider PHP class:

class CustomTypoScriptConditionProvider extends AbstractProvider
{
    public function __construct()
    {
        $this->expressionLanguageVariables = [
            'variableA' => 'valueB',
        ];
    }
}

In above example a new variable variableA with value valueB is added, this can be used within conditions:

[variableA === 'valueB']
    page >
    page = PAGE
    page.10 = TEXT
    page.10.value = Matched
[GLOBAL]

Additional functions

Additional functions can be provided through another class, which has to be returned by the example CustomTypoScriptConditionProvider PHP class:

class CustomTypoScriptConditionProvider extends AbstractProvider
{
    public function __construct()
    {
        $this->expressionLanguageProviders = [
            CustomConditionFunctionsProvider::class,
        ];
    }
}

The returned class will look like the following:

<?php

namespace Vendor\ExtensionName\TypoScript;

use Symfony\Component\ExpressionLanguage\ExpressionFunction;
use Symfony\Component\ExpressionLanguage\ExpressionFunctionProviderInterface;

class CustomConditionFunctionsProvider implements ExpressionFunctionProviderInterface
{
    public function getFunctions()
    {
        return [
            $this->getWebserviceFunction(),
        ];
    }

    protected function getWebserviceFunction(): ExpressionFunction
    {
        // TODO: Implement
    }
}

The class is already trying to return a new ExpressionFunction, but currently lacks implementation. That is the last step:

protected function getWebserviceFunction(): ExpressionFunction
{
    return new ExpressionFunction('webservice', function () {
        // Not implemented, we only use the evaluator
    }, function ($existingVariables, $endpoint, $uid) {
        return GeneralUtility::getUrl(
            'https://example.com/endpoint/'
            . $endpoint
            .  '/'
            . $uid
        );
    });
}

The first argument $existingVariables is an array of which each associative key corresponds to a registered variable.

  • request (TYPO3CMSCoreExpressionLanguageRequestWrapper)
  • applicationContext - string
  • typo3 . stdClass
  • tree - stdClass
  • frontend - stdClass
  • backend - stdClass
  • workspace - stdClass
  • page - array: page record

If you need an undefined number of variables, then you can write the same function in a variadic form:

// ...
}, function (...$args) {
    $existingVariables = $args['0'];
    // ...
}

All further arguments are provided by TypoScript. The above example could look like:

[webservice('pages', 10)]
    page.10 >
    page.10 = TEXT
    page.10.value = Matched
[GLOBAL]

If a simple string like a page title is returned, this can be further compared:

[webservice('pages', 10) === 'Expected page title']
    page.10 >
    page.10 = TEXT
    page.10.value = Matched
[GLOBAL]

Further information about ExpressionFunction can be found within Symfony Expression Language - Registering Functions