Create notification in controller:

$this->addFlash(
    'notice',
    'Your changes were saved!'
);

$this->addFlash is equivalent to $this->get('session')->getFlashBag()->add

Twig template to show notification:

{% for flash_message in app.session.flashbag.get('notice') %}
<div class="alert alert-success">
    {{ flash_message }}
</div>
{% endfor %}

 

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