JS复选下拉框取值

<?php
 if(isset($_POST["selectmultiple"])!=""){
 //$a=explode(",",$_POST["selectmultiple"]);
 //print_r($a);
 // for($i=0;$i<count($a);$i++){
 //  echo $a[$i]."<br/>";
 echo $_POST["selectmultiple"];
 // }
 }
?>
<script language=javascript>
 function getMultiple(ob)
 {
  var arSelected = new Array();
  arSelected = new Array();
  while (ob.selectedIndex != -1)
  {
   arSelected.push(ob.options[ob.selectedIndex].value);
   ob.options[ob.selectedIndex].selected = false;
  }
  // You can use the arSelected array for further processing.
  document.getElementById("selectmultiple").value=arSelected.toString();
  document.frmSelect.action="";
  document.frmSelect.submit();
 }
</script>
<form name='frmSelect' action="" method="post">
 <select name='numbers' multiple='multiple' style="height:180px;">
 <?php 
 for($i=1;$i<=10;$i++){
 ?>
 <option value="<?=$i;?>">　　<?=$i;?></option>
 <?php
 }
 ?>
 </select>
 <input type="hidden" name="selectmultiple" id="selectmultiple">
 <input type='button' value='Submit'  onclick="getMultiple(document.frmSelect.numbers);" />
</form>