全局变量 - 数据库连接？

Question

我想连接到一个数据库（MySQLi）只有一次，但我有问题这样做。

如何为整个脚本创建全局连接？有多个文件（index.php，/classes/config.class.php，/classes/admin.class.php等）。

我已经试过如下：

在：config.class.php

public static $config = array(); 
public static $sql; 

function __construct() { 
    // database 
    db::$config['host'] = 'localhost'; 
    db::$config['user'] = '_'; 
    db::$config['pass'] = '_'; 
    db::$config['db'] = '_'; 

    // connect 
    db::$sql = new mysqli(db::$config['host'], db::$config['user'], db::$config['pass'], db::$config['db']); 
} 

再次，在config.class.php

public function contectToDatabase($sql){ 
    $sql = new mysqli(db::$config['host'], db::$config['user'], db::$config['pass'], db::$config['db']); 
    $this->sql = $sql; 
} 

我用的是类的以下代码： $config = new db();

我真的很困惑a我怎么做到这一点。谁能帮忙？

---编辑--- 这是我的新config.class.php文件：

public static $config = array(); 
public static $sql; 

private static $db; 
private $connection; 

public function __construct() { 
    // database 
    db::$config['host'] = '_'; 
    db::$config['user'] = '_'; 
    db::$config['pass'] = '_'; 
    db::$config['db'] = '_'; 
    // connect 
    $this->connection = new mysqli(db::$config['host'], db::$config['user'], db::$config['pass'], db::$config['db']); 
} 
function __destruct() { 
    $this->connection->close(); 
} 
public static function getConnection() { 
    if($db == null){ 
     $db = new db(); 
    } 
    return $db->connection; 
} 

这就是我如何加载它：

require_once("classes/config.class.php"); 
$config = new db(); 
$sql = db::getConnection(); 

但是，在运行一个real_escape_string导致以下错误：

Warning: mysqli::real_escape_string() [mysqli.real-escape-string]: Couldn't fetch mysqli in /home/calico/_/_.com/_/index.php on line 20 

Warning: mysqli::query() [mysqli.query]: Couldn't fetch mysqli in /home/calico/_/_.com/_/index.php on line 28 

Answer 1

就个人而言，我使用一个单独的类。事情是这样的：

<?php 

class Database { 

    private static $db; 
    private $connection; 

    private function __construct() { 
     $this->connection = new MySQLi(/* credentials */); 
    } 

    function __destruct() { 
     $this->connection->close(); 
    } 

    public static function getConnection() { 
     if (self::$db == null) { 
      self::$db = new Database(); 
     } 
     return self::$db->connection; 
    } 
} 

?> 

就用$db = Database::getConnection();，无论我需要它。