这不起作用。旧参数丢失。我得到http://xxxx/temp/test.php?mode=compound
<form align="right" action="http://<? echo $_SERVER['SERVER_ADDR']."/temp/test.php?".$_SERVER['QUERY_STRING'];?>">
<? if ($_SESSION['mode']=="simple") { ?>
<input type="submit" value="Switch to compound mode">
<input type="hidden" name="mode" value="compound">
<? } else { ?>
<input type="submit" value="Switch to simple mode">
<input type="hidden" name="mode" value="simple">
<? } ?>
</form>