mssql_bind出错问题

今天玩着没事，用php连接mssql server 2005的存储过程，出现小的错误

代码如下，

$host="localhost";
	$user='sa';
	$password='01211107';
	$dbname='book';
	$link=mssql_connect($host,$user,$password) or die('link failure');
	if($link){
		mssql_select_db('book');
	}
	$stmt=mssql_init('cheng',$link);
	mssql_bind($stmt,'@ager', 25 ,SQLINT1,false,false,3);
	$sp=mssql_execute($stmt);
	while($row=mssql_fetch_assoc($sp)){
		print_r($row);
	}

存储过程为：

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go
ALTER procedure [dbo].[cheng]
@ager smallint
as
	begin 
		select count(*) as cou from student where age=@ager
	end

  

在xdebug调试下，提示

Fatal error: Only variables can be passed by reference in D:\php5\test.php on line 16

只有变量可以通过引用传递的意思

mssql_bind(),第三个参数必须是变量