我是 OOP 的新手，為什么我在其他文件中的類在我包含的其他類中找不到變量..？我嘗試發送變量 $db 但它給了我錯誤。第一課<?php//making Database connectionclass DBconnection{ public function __construct() { DEFINE("DB_USER", "root"); // username database DEFINE("DB_PASS", ""); // password database try { $db = new PDO("mysql:host=localhost;dbname=php_opdracht2", DB_USER, DB_PASS); //host & database name $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); echo "Connected successfully"; } catch (PDOException $e) { echo $e->getMessage(); } }}//running the class DBconnection$obj = new DBconnection();第二類（另一個 .php 文件）<?php//getting the database connectionrequire_once('DBconnection.php');//getting the data from the databaseclass Controller{ public function processing() { try { $query = "SELECT * FROM information"; $sth = $db->query($query); //why does it not find $db.. } catch (PDOException $e) { echo $e->getMessage(); } }}$obj3 = new Controller();$obj3->processing();
1 回答
慕村225694
TA貢獻1880條經驗 獲得超4個贊
在您的 DBconnection 類中，聲明一個公共變量來保存數據庫連接
<?php
//making Database connection
class DBconnection {
public $db;
public function __construct() {
DEFINE("DB_USER", "root"); // username database
DEFINE("DB_PASS", ""); // password database
try {
$this->db = new PDO("mysql:host=localhost;dbname=php_opdracht2", DB_USER, DB_PASS); //host & database name
$this->db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
echo "Connected successfully";
} catch (PDOException $e) {
echo $e->getMessage();
}
}
}
然后在另一個類中，訪問它如下
<?php
//getting the database connection
require_once('DBconnection.php');
//getting the data from the database
class Controller {
public function processing() {
try {
$connection = new DBconnection(); #call db class
$query = "SELECT * FROM information";
$sth = $connection->db->query($query); //access the db variable created in db class
} catch (PDOException $e) {
echo $e->getMessage();
}
}
}
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