PHP和MySQL错误：类mysqli_result的对象无法转换为字符串

Question

我收到错误：

Object of class mysqli_result could not be converted to string. 

代码：

<?php 
    $con=mysqli_connect("78.46.51.231","root","","multicraft_daemon"); 
    if (mysqli_connect_errno($con)){ 
    echo "Failed to connect to MySQL: " . mysqli_connect_error(); 
    } 

    $sql = ("select sum(`memory`) from `server`;"); 

    $result = mysqli_query($con, $sql); 

    echo $result; //$result is mysqli_result and can't be forced to string. 
?> 

什么是做这种正确的方法是什么？

Answer 1

您不能直接输出查询结果。使用：

$sql = ("select sum(`memory`) AS memTotal from `server`"); 
// Show used memory 
$result = mysqli_query($con, $sql); 
echo $result->fetch_object()->memTotal; 

$result该变量保存的对象（类型mysqli_result的），从中可以提取需要输出的标量。

Answer 2

$result是一个结果对象。从手册中获取mysqli_query()：

Returns FALSE on failure. For successful SELECT, SHOW, DESCRIBE or EXPLAIN queries mysqli_query() will return a mysqli_result object . For other successful queries mysqli_query() will return TRUE.