PHP避免使用全局$database与PDO连接

Question

我有下面的代码。我想要的是避免使用全局$db，因为我听说这是不好的做法，我正在寻找更健壮/实现良好的功能。

connection.php

<?php
try {
    $db = new PDO('mysql:host=127.0.0.1;dbname=blop', 'blop', 'root');
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (Exception $e) {
    $error = $e->getMessage();
    echo $error;
}
?>

Admin.php

<?php
class Admin {
    public function fetch_data() {
        global $db;
        $sql = "SELECT * FROM `people` ORDER BY `id` DESC";
        $result = $db->query($sql);
        return $result;
    }
    public function fetch_row_count() {
        global $db;
        $sql = "SELECT * FROM `people`";
        $result = $db->query($sql);
        $num_rows = $result->rowCount();
        return $num_rows;
    }
    public function deleteAll() {
        global $db;
        $deleteAll = $db->prepare("DELETE FROM `people`");
        $deleteAll->execute();
    }
    public function deleteData($id) {
        global $db;
        $id = $_POST['id'];
        $deleteData = $db->prepare("DELETE FROM `people` WHERE `id` = '$id'");
        $deleteData->execute();
    }
}
?>

Answer 1

依赖注入是指将类需要的所有依赖项(在本例中是PDO)传递给类。下面是一个使用构造函数注入的例子(我们将数据库传递给构造函数)。当实例化对象时，您需要这样做$admin = new Admin($db);而不是$admin = new Admin();

还请注意，在方法deleteData中，$id = $_POST['id'];行应该被删除，因为它不仅使用了另一个依赖项(post请求)，而且还覆盖了传递给方法的$id，使方法签名没有意义。

希望对你有帮助。

class Admin {
    protected $db;
    public function __construct(PDO $db) {
        $this->db = $db;
    }
    public function fetch_data() {
        $sql = "SELECT * FROM `people` ORDER BY `id` DESC";
        $result = $this->db->query($sql);
        return $result;
    }
    public function fetch_row_count() {
        $sql = "SELECT * FROM `people`";
        $result = $this->db->query($sql);
        $num_rows = $result->rowCount();
        return $num_rows;
    }
    public function deleteAll() {
        $deleteAll = $this->db->prepare("DELETE FROM `people`");
        $deleteAll->execute();
    }
    public function deleteData($id) {
        $deleteData = $this->db->prepare("DELETE FROM `people` WHERE `id` = '$id'");
        $deleteData->execute();
    }
}

Answer 2

引入依赖注入:

class Admin {
    protected $db;
    public function __construct(PDO $db) {
        $this->db = $db;
    }
    public function fetch_data() {
        ...
        $this->db->query(...);
        ...
    }
    ...
}
$pdo   = new PDO(...);
$admin = new Admin($pdo);
$admin->fetch_data();

很简单，真的。您只需显式地将所有外部依赖项传递给需要它的类。