小编Mic*_*ael的帖子

我试图让我的头围绕mysql.谁能告诉我为什么这个mysql查询不起作用？我收到以下错误:

警告:mysqli_error()预计在第11行的/home/freebet2/public_html/test.php中给出了1个参数0

test.php的

<?php
        require_once($_SERVER['DOCUMENT_ROOT'].'/includes/db.php');
        $conn = db_connect();
        $result = $conn->query("ALTER TABLE users ADD COLUMN refer_old INT(10) AFTER refer_id");

              if(!$result){
                 echo "Error with MySQL Query: ".mysqli_error();
             }
        ?>

db.php中

 <?php

    function db_connect() {
       $result = new mysqli('localhost', 'user', 'password', 'db');
       if (!$result) {
         throw new Exception('Could not connect to database server');
       } else {
         return $result;
       }
    }

    ?>

如果我将alter string更改为:$result = $conn->query("SELECT * FROM users refer_id");我出于某种原因没有错误.