怎么实现在select中选完以后在下一级select自动显示和上一级相关的数据行

<?phpif($_SERVER['REQUEST_METHOD'] == "POST") {  $d = array(    array(1,2,3,4),    array(11,12,13,14),    array(21,22,23,24),    array(31,32,33,34),    array(41,42,43,44),  );  foreach($d[$_POST['s1']] as $v) echo "<option value=$v>$v</option>";  exit;}?><script src=scripts/jquery-1.8.3.min.js></script><script>$(function() {  $('#s1').load(location.href, {s1 : 0});  $('#s1').change(function() {    $(this).next().load(location.href, {s1:$(this).val()});  });});</script><select name=s1 id=s1></select><select name=s2 id=s2></select>