Php 带有配置文件的单例数据库连接

下面是我的连接代码，它在没有配置文件（

.ini

文件）的情况下运行良好。但如果使用配置文件，则会出现以下错误：

致命错误：常量表达式在第13行的singletonDB.php中包含无效操作

但是正如您所看到的，变量

$dsn

、

$user

和

$pass

不是静态变量。我不明白为什么非静态变量会出现与静态变量相关的错误

我的最终目标是使用配置文件，同时只保留到DB的单例连接

<?php
$config = parse_ini_file("config.ini");
var_dump($config);
// Singleton to connect db.
class ConnectDb
{

    // Hold the class instance.
    private static $instance = null;

    private $pdo;

    private $dsn = $config['dsn_config'];

    private $user = $config['user_config'];

    private $pass = $config['password_config'];

    // The db connection is established in the private constructor.
    private function __construct()
    {
        echo nl2br("Inside constructor"); 
        $this->pdo = new PDO($this->dsn, $this->user, $this->pass);
        $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    }

    public static function getInstance()
    {
        if (! self::$instance) {
            self::$instance = new ConnectDb();
        }

        return self::$instance;
    }

    public function getConnection()
    {
        return $this->pdo;
    }
}

---

谢谢。

问题不在于

$dsn

、

$user

或

$pass

，而在于

$config

。您不能这样分配

$config

。如果将这些更改为字符串或其他值（int、array、bool），则会发现错误消失：

private $dsn  = false;  # All of these are 
private $user = [];     # are valid
private $pass = 1234;   # assignments

然后问题是如何分配

ini

args？一种常见的方法是在实例化类时只将其注入类的构造中：

class ConnectDb
{
    private static $instance = null;

    private $pdo;    
    private $dsn = '';
    private $user = '';
    private $pass = '';

    private function __construct($dsn, $user, $pass)
    {
        $this->dns = $dns;
        $this->user = $user;
        $this->pass = $pass;

        echo nl2br("Inside constructor"); 
        $this->pdo = new PDO($this->dsn, $this->user, $this->pass);
        $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    }
    ...etc.

使用：

<?php
$config = parse_ini_file("config.ini");
# Inject into the construct here
$Db = new ConnectDb($config['dsn_config'], $config['user_config'], $config['password_config']);

---

我不想在程序中的其他地方创建对象，因此根据@Rasclatt的解释，我将配置读取代码移到构造函数中，现在它工作正常。下面是更新的代码

文件名“singletonDB.php”

---

但是，我不确定这是否是一种好的编程方式。

谢谢您对Rasclatt的详细解释。但是，我不想在程序的其他地方创建对象。因此，根据您的解释，我只在构造函数中移动了读取代码的配置文件。我不知道这是否是一个好的方法。是的，这也有效。这样做有好处。它类似于使用defines，因为您可以随时创建connect，而无需首先解析ini并注入数组

<?php
$config = parse_ini_file("config.ini");
# Inject into the construct here
$Db = new ConnectDb($config['dsn_config'], $config['user_config'], $config['password_config']);

<?php
$config = parse_ini_file("config.ini");
# Create some defines
define('DB_DSN', $config['dsn_config']);
define('DB_USER', $config['user_config']);
define('DB_PASS', $config['password_config']);

class ConnectDb
{
    private static $instance = null;

    private $pdo;
    private $dsn = '';
    private $user = '';
    private $pass = '';

    private function __construct()
    {
        # Assign the constants here ALTHOUGH...
        # I don't know that there is a good reason to make these class 
        # variables. I would just put the constants into the construct of
        # the PDO below. I don't know that you are going to need to reference
        # these variables after you have created the PDO connection.
        $this->dns = DB_DSN;
        $this->user = DB_USER;
        $this->pass = DB_PASS;

        echo nl2br("Inside constructor"); 
        $this->pdo = new PDO($this->dsn, $this->user, $this->pass);
        $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    }
    ...etc.

<?php

// Singleton to connect db.
class ConnectDB
{

    // Hold the class instance.
    private static $instance = null;

    private $pdo;

    private $dsn = '';

    private $user = '';

    private $pass = '';

    // The db connection is established in the private constructor.
    private function __construct()
    {
//         $pdo = new PDO($dsn, $user, $password);
        $config = parse_ini_file("../config.ini");
        echo nl2br("var_dump ing config");
        var_dump($config);

        $this->dsn = $config['dsn_config'];
        $this->user = $config['user_config'];
        $this->pass = $config['password_config'];

        echo nl2br("Inside constructor"); 
        $this->pdo = new PDO($this->dsn, $this->user, $this->pass);
        $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    }

    public static function getInstance()
    {
        if (! self::$instance) {
            self::$instance = new ConnectDB();
        }

        return self::$instance;
    }

    public function getConnection()
    {
        return $this->pdo;
    }
}

require_once 'singletonDB.php';
$instance = ConnectDB::getInstance();
$conn = $instance->getConnection();
var_dump($conn);