函数内部的 mysqli/mysql 查询不起作用

问题描述

我正在尝试为我的网站构建一些功能，其中一些包括从mysql数据库中获取数据.当我在函数之外测试代码时它似乎工作正常.所以在这里，第一页:

I'm tryin to build some functions for a website of mine and some of them consist in fetching data from the mysql database. When I test the code outside of the function it seems to work properly. So here it is, The first page:

require('db.php');
require('functions.php');

$email = 'sample@gmail.com';

if (user_exists($email) == true){
 echo "Good news, this exists";
}

现在 db.php :

Now db.php :

$db = new MySQLi("localhost","test","test","test");
if ($db->connect_errno){
    echo "$db->connect_errno";
}

还有functions.php文件:

And the functions.php file:

function sanitize ($data){
    $db->mysqli_real_escape_string($data);
}
function user_exists($usermail){
    $usermail = sanitize($usermail);
    $query = $db->query("SELECT COUNT(userId) FROM users WHERE userEmail= '$usermail' ");
    $check = $query->num_rows;
    return ($check == 1) ? true : false;
}

访问第一个文件时遇到的错误是:

And the error I'm getting when accessing the first file is:

Notice: Undefined variable: db in C:xampphtdocsauctiorincfunctions.php on line 6

Fatal error: Call to a member function query() on a non-object in C:xampphtdocsauctiorincfunctions.php on line 6

所以我需要/包含了 db.php，其中 $db 是 mysqli 连接.在同一个文件(第一个文件)中，我调用位于 functions.php 的函数

SO I've required/included the db.php where $db is the mysqli connect. And within the same file(first file) I call the functions located at functions.php

先谢谢你，我很感激你的帮助，因为这让我很生气......

Thank you in advance, I'd appreciate your help as this is pissing me off......

推荐答案

你可能需要使用 global 关键字，否则 $db 被认为是局部范围内的 var.

You probably need to use the global keyword, otherwise $db is considered a var in local scope.

function sanitize ($data){
    global $db;
    $db->mysqli_real_escape_string($data);
}

function user_exists($usermail){
    global $db;
    $usermail = sanitize($usermail);
    $query = $db->query("SELECT COUNT(userId) FROM users WHERE userEmail= '$usermail' ");
    $check = $query->num_rows;
    return ($check == 1) ? true : false;
}

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