SimplePie_IRI::set_iri

		{
			$cache = array();
		}

		if ($iri === null)
		{
			return true;
		}
		elseif (isset($cache[$iri]))
		{
			list($this->scheme,
				 $this->iuserinfo,
				 $this->ihost,
				 $this->port,
				 $this->ipath,
				 $this->iquery,
				 $this->ifragment,
				 $return) = $cache[$iri];
			return $return;
		}

		$parsed = $this->parse_iri((string) $iri);
		if (!$parsed)
		{
			return false;
		}

		$return = $this->set_scheme($parsed['scheme'])
			&& $this->set_authority($parsed['authority'])
			&& $this->set_path($parsed['path'])
			&& $this->set_query($parsed['query'])
			&& $this->set_fragment($parsed['fragment']);

		$cache[$iri] = array($this->scheme,
							 $this->iuserinfo,
							 $this->ihost,
							 $this->port,
							 $this->ipath,
							 $this->iquery,
							 $this->ifragment,
							 $return);
		return $return;
	}

	/**
	 * Set the scheme. Returns true on success, false on failure (if there are
	 * any invalid characters).
	 *
	 * @param string $scheme