& quot;注意:未定义的变量:db& quot;使用PDO时 [英] "Notice: Undefined variable: db" when using PDO

问题描述

为了学习PDO，我编写了以下代码:

On my quest to learn PDO, I wrote this code:

$sql = 'SELECT * FROM category ORDER BY order_cat DESC';
foreach ($db->query($sql) as $row)
{
    echo "<input type='radio' name='category' value='$row[id]'>$row[name]<br />";
}

然后我将其封装为如下所示的函数:

I then encapsulated it into a function like so:

function GetCategory()
{
    $sql = 'SELECT * FROM category ORDER BY order_cat DESC';
    foreach ($db->query($sql) as $row)
    {
        echo "<input type='radio' name='category' value='$row[id]'>$row[name]<br />";
    }
}

我这样称呼它:

echo GetCategory();

但是，当我这样做时，会出现以下错误:

However, when I do that, I get these errors:

注意:未定义变量:db
致命错误:在非对象上调用成员函数query()

Notice: Undefined variable: db
Fatal error: Call to a member function query() on a non-object

我不知道我在想什么；我在配置文件中声明$db如下:

I don't know what I'm missing; I'm declaring $db in my configuration file like so:

$db = new PDO("mysql:host=$localhost;dbname=$namedb;charset=utf8", $userdb, $passdb);

推荐答案

在函数内部使$ db全局化.

Make the $db global as you are inside a function.

function GetCategory()
{
global $db;
...
}

如果之前已经定义过...

If it has been defined before of course...

这篇关于& quot;注意:未定义的变量:db& quot;使用PDO时的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！