<strong>Explanation:</strong>

<table style="margin: 5px 0;">
    <thead>
        <tr>
            {% for label in data[0]|keys %}
                <th>{{ label }}</th>
            {% endfor %}
        </tr>
    </thead>
    <tbody>
        {% for row in data %}
        <tr>
            {% for item in row %}
                <td>{{ item }}</td>
            {% endfor %}
        </tr>
        {% endfor %}
    </tbody>
</table>
<strong>Explanation:</strong>

<table style="margin: 5px 0;">
    <thead>
        <tr>
            {% for label in data[0]|keys %}
                <th>{{ label }}</th>
            {% endfor %}
        </tr>
    </thead>
    <tbody>
        {% for row in data %}
        <tr>
            {% for key, item in row %}
                <td>{{ 'possible_keys' == key ? item|replace({',': ', '}) : item }}</td>
            {% endfor %}
        </tr>
        {% endfor %}
    </tbody>
</table>

Split indexes returned by mysql
Split indexes returned by mysql

Currently PDO returns indexes from MySQL Explain query separated by comma without space, which leads to a very long lines in Symfony profiler.

[] Check that other DBs will handle this
