PHP调用MYSQL存储过程求助

错误信息:
Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given in D:\RUIOA\webroot\MyPHP\News\test.php on line 37


PHP:
<?php
$conn = mysqli_connect("localhost","root","chen");
mysqli_select_db($conn,"test");
$result = mysqli_query($conn,"call list();"); ==============>这里换成"select * from users;"就正常读出数据
while($row = mysqli_fetch_array($result)){
echo $row[1]."&nbsp;&nbsp;".$row[2]."&nbsp;&nbsp;".$row[2]."<br>";
}
?>

Mysql:
CREATE PROCEDURE list()
BEGIN
select * from users;
END;



mysqli与mysql都用过了,情况都是一样,用SQL语句就没问题,但是调用存储过程就不行

$result = mysqli_query('select * from users', $conn);//$conn是mysql_connect返回值(可有可无)