PHP导出Excel动态文件名

<?php
header("content-type:application/vnd.ms-excel; charset=gbk");
header("content-disposition:attachment;filename=exceltest".$_GET[id]."muzi.xls");
$link=mysql_connect('localhost','root','muzi');
if($link){
    mysql_select_db('exceltest',$link);
    mysql_query("set names 'gbk'");
    //echo "数据库教程连接已经成功！";
}else{
     echo "数据库连接失败！";
}
echo "编号"."/t";
echo "姓名"."/t";
echo "姓别"."/n"; 
$id = $_GET[id];
$sql="select * from downtest where id ='".$id."'";
$query=mysql_query($sql);
while($rs=mysql_fetch_array($query)){
          echo $rs[id]."/t";
          echo $rs[name]."/t";
          echo $rs[sex]."/n";             
}

  ?>