<?php
class CachedSandBoxParser extends SandBoxParser
{
  protected
    $cache = array();

  public function convertWikiText($wikiText, $wgTitle = ''){
    $key = sha1($wikiText . $wgTitle);
    if( ! array_key_exists($key, $this->cache)){
      $content = parent::convertWikiText($wikiText, $wgTitle);
      $this->cache[$key] = $content;
    }
    return $this->cache[$key];
  }
}