View file phpBB3/config/default/container/services_language.yml

services:
    language.helper.language_file:
        class: phpbb\language\language_file_helper
        arguments:
            - '%core.root_path%'

    language:
        class: phpbb\language\language
        arguments:
            - '@language.loader'

    language.loader_abstract:
        abstract: true
        class: phpbb\language\language_file_loader
        arguments:
            - '%core.root_path%'
            - '%core.php_ext%'

    language.loader:
        parent: language.loader_abstract
        calls:
            - [set_extension_manager, ['@ext.manager']]