php - PHP 中包含类时无法调用 MySQL

Question

我在包含时遇到问题。我正在写某种博客，此时它看起来像这样:

index.php
article.php
class/art.class.php

让我们关注article.php，它看起来像这样:

<?php
$mysqli = new mysqli("","","",""); // here are my connection details
if ($mysqli->connect_error) {
    die('Connect Error (' . $mysqli->connect_errno . ') '
            . $mysqli->connect_error);
}

$mysqli->query("SET NAMES 'utf8'");
require("class/art.class.php");
$art = new Article();
print_r($art->get_art(trim($_GET['id'])));
$mysqli->close();
?>

art.class.php 是这样的:

<?php
class Article {
    function get_art($id) {
        if(!is_numeric($id)) {
            header("Location: index.php");
            die("<h2>ID isn't numeric, cannot go on.</h2>'");
        }
        if($result = $mysqli->query("SELECT * FROM `articles` WHERE id='$id';")) {
            while($row = $result->fetch_array(MYSQLI_ASSOC)) {
                $art = $row;
            }
            $result->close();
        }
        return $art;
    }
}
?>

问题是来自 MySQL 的响应。抱歉，我的意思是没有回应。并且没有错误。我发现我需要将 mysql 连接代码添加到类代码中。但为什么？我如何连接到数据库一次并从任何地方调用它，甚至从包含的类中调用它？如果我的英语不好，很抱歉..

Answer 1

Article 类中的 get_art 函数无法访问其范围之外的变量:请参阅答案 here .

为了解决您的问题，您可以在实例化 $mysqli 对象时将其传递给 Article 类的构造函数来提供对它的访问:

文章.php:

$mysqli = new mysqli("","","",""); // your connection details
$art = new Article($mysqli);

art.class.php:

class Article {

    protected $mysqli;

    public function __construct($mysqli) {
        $this->$mysqli = $mysqli;
    }

    function get_art($id) {

        // Replace $mysqli with $this->mysqli everywhere you need to
        // make database calls

    }
}