public static function signInAs($username)
	{
		$ip = self::getClientIp();
		$ua = ( isset( $_SERVER['HTTP_USER_AGENT'] ) ) ? $_SERVER['HTTP_USER_AGENT'] : '';
		$ts = date("U");
		$cu = self::getCurrentUsername();

		self::sessionWrite( array( 'username' => $username ) );
		self::reload();

		self::log( 'signinas ' . $username , $cu, $ts , $ip , $ua );
		self::save();

		return self::$auth['users'][ $username ];
	}