test_app/public/phpMyAdmin4.8.5/templates/table/relation/relational_dropdown.twig

<select name="{{ name }}" title="{{ title }}">
    <option value=""></option>
    {% set seen_key = false %}
    {% for value in values %}
        <option value="{{ value }}"
            {%- if foreign is not same as(false) and value == foreign %}
                selected="selected"
                {%- set seen_key = true -%}
            {%- endif %}>
            {{ value }}
        </option>
    {% endfor %}
    {% if foreign is not same as(false) and not seen_key %}
        <option value="{{ foreign }}" selected="selected">
            {{ foreign }}
        </option>
    {% endif %}
</select>