webapp/public/image.php

<?php

require_once('../library/icon.php');

if (isset($_GET['hash'])) {

  header("Content-Type: image/jpeg");

  $filename = dirname(__FILE__) . '/../cache/' . $_GET['hash'] . '.jpeg';

  if (!file_exists($filename)) {

    $icon = new Icon();

    file_put_contents($filename, $icon->generateImageResource(md5($_GET['hash']), 60, 60, false));
  }

  echo file_get_contents($filename);
}