Question

我是php新手，我想做的是在课堂外获取$ conn变量。我从另一个文件中包含了这个文件并尝试使用$dbConfig->conn来获取变量，但它什么也没有返回。

这是我在另一页上的通知。注意：未定义的变量：第8行的C：\ xampp \ htdocs \ Chat \ login.php中的dbConfig

<?php 
class dbConfig {
public $host;
public $username;
public $password;
public $dab;
public $conn;

public function dbConnect() {
$conn = mysqli_connect($this->host,$this->username,$this->password);

if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}
else{
    echo "Connected successfully to server";
}

$db_selected = mysqli_select_db($conn, $this->dab);

if (!$db_selected) {
    // if the given database doesn't exists
    // creates new database with that name
    $db_sql = 'CREATE DATABASE chatapp';

    // verify the database is created
    if (mysqli_query($conn, $db_sql)){
        echo "Database chatapp already exists or created successfully\n";
    } else {
        echo 'Error creating database: ' . mysqli_error() . "\n";
    }
}

// creating tables
$table_sql = "CREATE TABLE IF NOT EXISTS users (".
        "uid INT PRIMARY KEY AUTO_INCREMENT,".
        "username VARCHAR(30) UNIQUE,".
        "password VARCHAR(50),".
        "name VARCHAR(100),".
        "email VARCHAR(70) UNIQUE); ";

// verify the table is created
    if (mysqli_query($conn, $table_sql)) {
        echo "Table: users already exists or created successfully\n";
    } else {
        echo 'Error creating table: ' . mysqli_error($table_sql) . "\n";
    }
}
}

$obj = new dbConfig();

$obj->host = 'localhost';
$obj->username = 'root';
$obj->password = '';
$obj->dab = 'chatapp';
$obj->dbConnect();

Answer 1

您已实例化$obj而非$dbConfig，因此请使用$obj
在课程中，您需要将$conn指定为对象属性

$this->conn = mysqli_connect($this->host,$this->username,$this->password);

然后在课程中使用$this->conn。

Answer 2

问题是你如何在方法中引用类变量。看：

public function dbConnect() {
    $conn = mysqli_connect($this->host,$this->username,$this->password);
    ...

在这里，您要创建一个名为$conn的局部变量（仅限于当前方法的范围）。由于您正在使用该课程的实例，因此您需要使用$this访问您的班级成员：

$this->conn = mysqli_connect(...);

请查看the docs了解更多信息。

访问类php内部定义的公共变量

2 个答案: