public function get_categories()
	{
		$categories = array();

		$type = 'category';
		foreach ((array) $this->get_item_tags(SIMPLEPIE_NAMESPACE_ATOM_10, $type) as $category)
		{
			$term = null;
			$scheme = null;
			$label = null;
			if (isset($category['attribs']['']['term']))
			{
				$term = $this->sanitize($category['attribs']['']['term'], SIMPLEPIE_CONSTRUCT_HTML);
			}
			if (isset($category['attribs']['']['scheme']))
			{
				$scheme = $this->sanitize($category['attribs']['']['scheme'], SIMPLEPIE_CONSTRUCT_HTML);
			}
			if (isset($category['attribs']['']['label']))
			{
				$label = $this->sanitize($category['attribs']['']['label'], SIMPLEPIE_CONSTRUCT_HTML);
			}
			$categories[] = $this->registry->create('Category', array($term, $scheme, $label, $type));
		}
		foreach ((array) $this->get_item_tags(SIMPLEPIE_NAMESPACE_RSS_20, $type) as $category)
		{
			// This is really the label, but keep this as the term also for BC.
			// Label will also work on retrieving because that falls back to term.
			$term = $this->sanitize($category['data'], SIMPLEPIE_CONSTRUCT_HTML);
			if (isset($category['attribs']['']['domain']))
			{
				$scheme = $this->sanitize($category['attribs']['']['domain'], SIMPLEPIE_CONSTRUCT_HTML);
			}
			else
			{
				$scheme = null;
			}
			$categories[] = $this->registry->create('Category', array($term, $scheme, null, $type));
		}

		$type = 'subject';
		foreach ((array) $this->get_item_tags(SIMPLEPIE_NAMESPACE_DC_11, $type) as $category)
		{
			$categories[] = $this->registry->create('Category', array($this->sanitize($category['data'], SIMPLEPIE_CONSTRUCT_HTML), null, null, $type));
		}
		foreach ((array) $this->get_item_tags(SIMPLEPIE_NAMESPACE_DC_10, $type) as $category)
		{
			$categories[] = $this->registry->create('Category', array($this->sanitize($category['data'], SIMPLEPIE_CONSTRUCT_HTML), null, null, $type));
		}

		if (!empty($categories))
		{
			return array_unique($categories);
		}
		else
		{
			return null;
		}
	}