Twig Extension to replace files with thumbnails

TwigExtension.php

<?php

namespace MyApp\Twig;

use Twig_Extension;
use Twig_SimpleFilter;

class TwigExtension extends Twig_Extension
{
    public $app;

	  public function __construct($app)
	  {
	      $this->app = $app;
	  }

	  public function getName()
	  {
	      return 'myappTwig';
	  }

	  public function getFilters()
	  {
	      return [
            new Twig_SimpleFilter('replace_thumbnails', [$this, 'replaceWithThumbnails']),
	   	  ];
	  }

    public function replaceWithThumbnails($text)
    {
        $doc = new DOMDocument('1.0', 'UTF-8');
        $doc->strictErrorChecking = true;
        $doc->standalone = true;
        $doc->xmlStandalone = true;
        $doc->formatOutput = true;
        $doc->loadHTML($text, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);
        $allImageNodes = $doc->getElementsByTagName("img");

        foreach($allImageNodes as $searchNode)
        {
            $src = $searchNode->getAttribute('src');
            if (strpos($src, '/files/') !== false) {
                $width = $searchNode->getAttribute('width') ?: 1000;
                $height = $searchNode->getAttribute('height') ?: 1000;
                $src = preg_replace('#(.*)(/files/)(.*)#', '$1/thumbs/'.$width.'x'.$height.'c/$3', $src);
                $searchNode->setAttribute('src', $src);
                $searchNode->removeAttribute('width');
                $searchNode->removeAttribute('height');
                $doc->importNode($searchNode);
            }
        }

        return $doc->saveHTML();
  }


}