获取checkbox 组成字符串

<input type="checkbox" id="goods_server_name" name="goods_server_name[]" value="1 "  >1

<input type="checkbox" id="goods_server_name" name="goods_server_name[]" value="2 "  >2

<input type="checkbox" id="goods_server_name" name="goods_server_name[]" value="3 "  >3

<input type="checkbox" id="goods_server_name" name="goods_server_name[]" value="4 "  >4

$str_tag="";
$s=$_POST['goods_server_name'];
for($i=0;$i<count($s);$i++){
if($i==0){
$str_tag = $s[$i];
}else{
$str_tag = $str_tag .",".$s[$i];
}
}