php - 为什么我的 pdo 变量始终未定义？

Question

这个问题已经有答案了:

PDO Fatal error: Call to a member function prepare() on a non-object (3 个回答)

Reference: What is variable scope, which variables are accessible from where and what are "undefined variable" errors? (3 个回答)

Call to a member function prepare() on a non-object PHP Help [duplicate] (8 个回答)

已关闭 5 年前。

我有两个 php 文件，一个是用于 PDO 连接的文件，另一个是在此连接上提交准备好的语句的文件:

PDO 连接:

class Connection {

protected $user = "ni873420_2sql1";
protected $pass = "#";
public $pdo_log;

public function __construct() {

        try {

            $pdo_log = new PDO('mysql:host=localhost;dbname=ni873420_2sql1', 
                               $this->user, $this->pass);

        }
        catch (Exception $e) {

            die($e);

        }
    }
}

这是我创建准备好的语句的函数:

    public static function getInfobyEmailUsername($argemailusername) {

    $get_info_query = "SELECT * FROM user WHERE email = ? OR username = ?";

    $conn = new Connection();
    $getinfostmt = $conn->pdo_log->prepare($get_info_query);
    $getinfostmt->execute(array($argemailusername, $argemailusername));

    $userinfo = $getinfostmt->fetch(PDO::FETCH_ASSOC);

    if (!empty ($userinfo)) {
        return $userinfo;
    } else {
        return false;
    }

    }

但我不断收到错误:

Fatal error: Call to a member function prepare() on null

我在任何地方都找不到解决方案，任何人都可以帮助我解决这个问题，或者至少发送一个链接，让我可以找到解决方案吗？

谢谢!

Answer 1

在构造函数中，使用公共(public)变量$pdo_log

  $this->pdo_log = new PDO('mysql:host=localhost;dbname=ni873420_2sql1', 
                           $this->user, $this->pass);