LanguageService 

This class is used to translate strings in plain PHP. For examples see Localization in PHP. A LanguageService should not be created directly, therefore its constructor is internal. Create a LanguageService with the LanguageServiceFactory.

In the backend context a LanguageService is stored in the global variable $GLOBALS['LANG']. In the frontend a LanguageService can be accessed via the contentObject:

<?php

use Psr\Http\Message\ServerRequestInterface;
use TYPO3\CMS\Core\Localization\LanguageServiceFactory;

final class ExampleController
{
    private ServerRequestInterface $request;

    public function __construct(
        private readonly LanguageServiceFactory $LanguageServiceFactory,
    ) {}

    public function processAction(
        string $content,
        array $configurations,
        ServerRequestInterface $request,
    ): string {
        $this->request = $request;

        // ...
        $content .=  $this->getTranslatedLabel(
            'LLL:EXT:my_extension/Resources/Private/Language/locallang.xlf:labels.exampleLabel',
        );
        // ...

        return $content;
    }

    private function getTranslatedLabel(string $key): string
    {
        $language =
            $this->request->getAttribute('language')
                ?? $this->request->getAttribute('site')->getDefaultLanguage();
        $languageService = $this->LanguageServiceFactory
            ->createFromSiteLanguage($language);

        return $languageService->sL($key);
    }
}

In CLI context $GLOBALS['LANG'] is also not available and has to be instantiated manually.

class LanguageService

Fully qualified name

\TYPO3\CMS\Core\Localization\LanguageService

Main API to fetch labels from XLF (label files) based on the current system language of TYPO3. It is able to resolve references to files + their pointers to the proper language. If you see something about "LLL", this class does the trick for you. It is not related to language handling of content, but rather of labels for plugins.

Usually this is injected into $GLOBALS['LANG'] when in backend or CLI context, and populated by the current backend user. Do not rely on $GLOBAL['LANG'] in frontend, as it is only available under certain circumstances!

As TYPO3 internally does not match the proper ISO locale standard, the "locale" here is actually a list of supported language keys, (see Locales class), whereas "English" is always the fallback ("default language").

Further usages on setting up your own LanguageService in BE:

$languageService = GeneralUtility::makeInstance(LanguageServiceFactory::class)
    ->createFromUserPreferences($GLOBALS['BE_USER']);

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public lang

This is set to the language which is currently running for the user

sL ( ?string $input)

Main and most often used method.

Resolve strings like these:

'LLL:EXT:core/Resources/Private/Language/locallang_core.xlf:labels.depth_0'
'LLL:core.messages:labels.depth_0'
'core.messages:labels.depth_0'  // LLL: prefix is optional

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This looks up the given .xlf file path or translation domain in the 'core' extension for label labels.depth_0

The LLL: prefix is optional. If the input contains a colon (:), it will be treated as a label reference. If no colon is found, the input string is returned as-is (constant non-localizable label).

Only the plain string contents of a language key, like "Record title: %s" are returned. Placeholder interpolation must be performed separately, for example via sprintf(), like LocalizationUtility::translate() does internally (which should only be used in Extbase context)

Example: Label is defined in EXT:my_ext/Resources/Private/Language/locallang.xlf as:

<trans-unit id="downloaded_times">
    <source>downloaded %d times from %s locations</source>
</trans-unit>

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The following code example assumes $this->request to hold the current request object. There are several ways to create the LanguageService using the Factory, depending on the context. Please adjust this example to your use case:

$language = $this->request->getAttribute('language');
$languageService =
  GeneralUtility::makeInstance(LanguageServiceFactory::class)
  ->createFromSiteLanguage($language);
$label = sprintf(
     $languageService->sL(
         'LLL:EXT:my_ext/Resources/Private/Language/locallang.xlf:downloaded_times'
     ),
     27,
     'several'
);

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This will result in $label to contain 'downloaded 27 times from several locations'.

param $input

Label key/reference

Returns

string

overrideLabels ( string $fileRef, array $labels)

Define custom labels which can be overridden for a given file. This is typically the case for TypoScript plugins.

param $fileRef

the fileRef

param $labels

the labels

getLocale ( )

Returns

?\TYPO3\CMS\Core\Localization\Locale