Flash Message

flash_msg.txt

// controller delete action:
use Doctrine\DBAL\Exception\ForeignKeyConstraintViolationException;
...
try {
    $em->remove($entity);
    $em->flush();
} catch(ForeignKeyConstraintViolationException $e) {
    $this->addFlash('warning', 'This item is in use by related entities and cannot be deleted.');
}


// twig (Foundation 5):
{% for flash_message in app.session.flashBag.get('warning') %}
    <div data-alert class="alert-box warning">
        {{ flash_message|raw }}
        <a href="#" class="close">&times;</a>
  </div>
{% endfor %}

// twig (Foundation 6):
{% for flash_message in app.session.flashBag.get('warning') %}
    <div class="callout warning" data-closable>
        {{ flash_message|raw }}
        <button class="close-button" aria-label="Dismiss alert" type="button" data-close>
            <span aria-hidden="true">&times;</span>
        </button>
    </div>
{% endfor %}