public function saveFontFamilies()
    {
        // replace the path to the DOMPDF font directories with the corresponding constants (allows for more portability)
        $cacheData = sprintf("<?php return array (%s", PHP_EOL);
        foreach ($this->fontLookup as $family => $variants) {
            $cacheData .= sprintf("  '%s' => array(%s", addslashes($family), PHP_EOL);
            foreach ($variants as $variant => $path) {
                $path = sprintf("'%s'", $path);
                $path = str_replace('\'' . $this->getOptions()->getFontDir() , '$fontDir . \'' , $path);
                $path = str_replace('\'' . $this->getOptions()->getRootDir() , '$rootDir . \'' , $path);
                $cacheData .= sprintf("    '%s' => %s,%s", $variant, $path, PHP_EOL);
            }
            $cacheData .= sprintf("  ),%s", PHP_EOL);
        }
        $cacheData .= ") ?>";
        file_put_contents($this->getCacheFile(), $cacheData);
    }