如何查询mysql里面的有多少条记录

$sql = "SELECT COUNT(*) as total FROM man_hours WHERE uid = {$uid}";
$rs = $conn->query($sql);

然后我写的是

$rows = mysqli_fetch_array($rs);

他这里就报错了

Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, bool given in C:\website\Apache24\htdocs\readexcel\public\tamplate\gongshi_total.php on line 69
我在phpmyadmin里面执行了一下

SELECT COUNT(*) AS total FROM man_hours WHERE uid = 'S5955'

获得的结果是
total
2

php版本是7.3.2
mysql版本是8.

好吧，是我语法有误

正常应该是

$sql = "SELECT COUNT(*) as total FROM man_hours WHERE uid = '{$uid}'";
$rs = $conn->query($sql);
if($rs){
    whlie ($row = mysqli_fetch_row($rs)){
        $total = $row[0];
    }
}