MaxTaggedPostsCountExtension.php

<?php

namespace Anyt\BlogBundle\Twig;

class MaxTaggedPostsCountExtension extends \Twig_Extension
{
  public function getFunctions()
  {
    return array(
      new Twig_SimpleFunction('getTagWeight', 'getTagWeight'),
    );
  }

  /**
    * maxWeight equals to available fonts sizes count
    */
  private $maxWeight;

  /**
    * entity manager
    */
  private $em;

  /**
    * doctrine 2 cacheDriver 
    * http://docs.doctrine-project.org/en/latest/reference/caching.html
    */
  private $cacheDriver;

  function getMaxTaggedPostsCount() {
    if ($maxTaggedPostsCount = $cacheDriver->fetch('max_tagged_posts_count')) {
      return $maxTaggedPostsCount;
    }
    $return $em->getRepository('DemoBundle:Tag')->getMaxTaggedPostsCount(); 
    // getMaxTaggedPostsCount() contains DQL "SELECT MAX(t.taggedPostsCount) from AnytBlogBundle:Tag as t"
  }

  function getTagWeight(Tag $tag) {
    return ceil( $tag->getTaggedPostsCount() * $this->maxWeight / $this->getMaxTaggedPostsCount() );
  }
}