Example of flood control using REDIS (Predis vía Symfony SNCRedisBundle)

CommentListener.php

<?php

namespace Foo/Bar/Event/Observer/CommentSubscriber;

// ...
// Use statements, constructor, boring code...
// ...

// Our callable wich listen for new comment attempt
public function onNewComment(FilterCommentEvent $event)
{
  $comment = $event->getComment();
  $user = $comment->getUser();

  // ...

  // If there are more than 10 living keys then the user is trying to flood us
  if(count($this->redisClient->keys('user:' . $user->getId() ':comments:attempt:*')) > 10)
  {
    throw new \Exception('Comments limit reached');
  }
}

CommentManager.php

<?php

namespace Foo/Bar/Model/Manager;

// ...
// Use statements, constructor, boring code...
// ...

// Our callable wich saves a new comment
public function save(Comment $comment)
{
  $event = new CommentEvent();
  $event->setComment($comment);

  // Raise our event
  $this->dispatcher->dispatch('foo.bar.comment.new',$event);

  // ...
  // We save our comment at db
  // ...
  
  // We register the comment attempt with a unique key and a foo value. It will expire
  // after 300 seconds (5 minutes)
  $redisKey = 'user:' . $comment->getUser()->getId() . ':comments:attempt:' . uniqid();
  $this->redisClient->set($redisKey,'foo');
  $this->redisClient->expire($redisKey,300);
}