setTraverser example

    public function __construct($dom, $out, RulesInterface $rules, $options = array())
    {
        $this->dom = $dom;
        $this->out = $out;
        $this->rules = $rules;
        $this->options = $options;

        $this->rules->setTraverser($this);
    }

    /** * Tell the traverser to walk the DOM. * * @return resource $out Returns the output stream. */
    public function walk()
    {
        if ($this->dom instanceof \DOMDocument) {
            $this->rules->document($this->dom);
        }