有结果集的mysqli函数获取行数和列数

<?php
    $mysqli=new mysqli("localhost", "root", "123456", "xsphpdb");

    if(mysqli_connect_errno()){
        echo "错误：".mysqli_connect_error();
        exit;
    }

    //执行select语句，返回来的就是结果集（对象）

    $sql="select id,name from shops where id <50";

    $result=$mysqli->query($sql);

    $rows=$result->num_rows;
    $cols=$result->field_count;

    echo "表中{$rows}行，{$cols}列<br>";

    $mysqli->close();