_header.twig

<div id="header">
    <form id="SelectLang" class="pure-form" method="get">
    {% if not hideLanguageBar %}
        <div id="languagebar" class="right">
    {% for name, value in queryParams %}
        {%- if value -%}
            <input type="hidden" name="{{ name }}" value="{{ value }}" />
        {%- else %}
            <input type="hidden" name="{{ name }}" />
        {% endif %}
    {% endfor %}

        <select  class="pure-input-1-4 language-menu selectize" name="language" id="language_selector">
    {% for key, lang in languageBar -%}
        {%- if key == currentLanguage -%}
            <option value="{{ key }}" selected="selected">{{ lang.name }}</option>
        {%- else -%}
            <option value="{{ key }}">{{ lang.name }}</option>
        {%- endif -%}
    {% endfor %}
        </select>
        </div>
    {% endif %}
    </form>
</div>