：mysql_fetch_row(): supplied argument is not a valid MySQL result resource _PHP

求救：mysql_fetch_row(): supplied argument is not a valid MySQL result resource
<?php

function db_connect()
{
   $result = new mysqli('localhost', 'root', '654321', 'smsprj');
   //$result = new mysqli('localhost', 'root', '654321');
   if (!$result)
   {
     throw new Exception('Could not connect to database server');
   }
   else
   {

     return $result;
   }
}

?>

$conn = db_connect();
$sql = $conn->query("SELECT * FROM user");

if (!$sql)
{
echo ("wrong");
}
else
{
echo "<table>";
echo "<tr><td>userid</td><td>name</td><td>pssword</td><td>maxsmscount</td><td>maxuseday</td><td>leftday</td><td>leftsmscount</td></tr>";
while( $row = mysql_fetch_row($sql) )
{
echo "<tr><td>$row[0]</td><td>$row[1]</td><td>$row[2]</td><td>$row[3]</td><td>$row[4]</td><td>$row[5]</td><td>$row[6]</td></tr>";
}
}
我的目的是将数据库中的所有用户信息显示出来
可这段程序老是报错，不知道什么原因
求大侠帮助，小弟不胜感激

mysql_fetch_row

------解决方案--------------------
db_connect 中是这样的
$result = new mysqli('localhost', 'root', '654321', 'smsprj');

所以要这样查询
$sql = $conn->query("SELECT * FROM user");

要这样读取
while( $row = $sql->fetch_row())