Manually switch _locale in symfony 4

Question

I\'m absolutely stuck in getting a solution to manually switch the _locale variable in Symfony 4.

I followed these steps, but now I have absolutely no idea

Answer 1

The answer is slightly different from this answer which is not applicable in Symfony 4. Start with editing the services.yaml file in the config directory.

{# project/config/services.yaml}

# ...
parameters:
    # ...
    app_locales: [nl_NL, en_EN]

twig:
    # ...
    globals:
        locales: %app_locales%
        # ...

Then add a template to integrate the switch button somewhere in your base template.

{# project/templates/_locale_switcher.html.twig #}

{% set route = app.request.attributes.get('_route') %}
{% set route_params = app.request.attributes.get('_route_params') %}
{% set params = route_params|merge(app.request.query.all) %}

{# You may want to not print a flag/link for current view, the "if" here let 
you handle it #}

{% for locale in locales if locale != app.request.locale %}

    <li>
        <a href="{{ path(route, params|merge({ _locale: locale })) }}">
            <img src="{{ asset('img/flags/' ~ locale ~ '.jpg') }}" alt="{{ 
locale }}">
        </a>
    </li>

{% endfor %}

And finally integrate this brandnew template in your base template.

{# project/templates/base.html.twig #}

{% include '_locale_switcher.html.twig' %}

EDIT for Symfony 4.3.4+

As per the answer of Charles beneath, the locales value in services.yaml file should be inserted with quotes to avoid an unvalid YAML error:

{# project/config/services.yaml}

# ...
parameters:
    # ...
    app_locales: [nl_NL, en_EN]

twig:
    # ...
    globals:
        locales: "%app_locales%"
        # ...