PHP 和 MySQL 错误：类 mysqli_result 的对象无法转换为字符串 [重复]

我收到错误：

mysqli_result 类的对象无法转换为字符串。

Code:

<?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.
?>

这样做的正确方法是什么？

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;

The $result变量保存一个对象（类型为 mysqli_result），您可以从中获取需要输出的标量。