php 多選框 js限制多選

<script>
 function choose(obj){   //限制多選 只能選一個
  var ss= document.getElementsByName("id");
  for (var i = 0; i < ss.length; i++) {
   ss[i].checked = false;
  }
   obj.checked = true;
 }

</script>

<?php foreach ($info as  $key){ ?>
<tr>
<td><input type="checkbox" name="id" onclick="choose(this)"  checked='checked' value="<?php echo $key->id;?>"></td>
</tr>
<?php }?>