Class 无法从其他类获取mysqli标识符

我有两个类：一个用于sql，另一个用于身份验证。这些是单独的文件，只能由自动加载程序在另一个文件index.php中组合在一起。sql类如下所示：

class aF_sql {
    public static $open;
    public static $char;
    public static $close;

    public static function open() {
        global $config;

        self::$open = mysqli_connect($config['aF_sql_host'], $config['aF_sql_user'], $config['aF_sql_pass'], $config['aF_sql_data']);
        if(!self::$open) {
            die('<b>ERROR (/core/sql/1): Could not initialize database connection</b>');
        }

        self::$char = mysqli_set_charset(self::$open, $config['aF_sql_char']);
        if(!self::$char) {
            die('<br>ERROR (/core/sql/2): Could not set database charset</br>');
        }

        return TRUE;
    }

    public static function close() {
        self::$close = mysqli_close(self::$open);
        if(!self::$close) {
            die('<b>ERROR (/core/sql/3): Could not close database connection');
        }

        return TRUE;
    }
}

错误是这样说的：警告：mysqli\u real\u escape\u字符串期望参数1为mysqli，如果给定空值。。。我应该使用什么作为能够执行查询的标识符？正如您所知，mysqli需要连接标识符

---

非常感谢

好的，我想出来了！我没有在类中返回TRUE，而是返回self:：$open。这样，我就可以在软件中的任何地方使用aF_sql:：$open，它引用连接标识符。换句话说，它不起作用，因为我没有在类中返回变量

class aF_sql {
public static $open;
public static $char;
public static $close;

public static function open() {
    global $config;

    self::$open = mysqli_connect($config['aF_sql_host'], $config['aF_sql_user'], $config['aF_sql_pass'], $config['aF_sql_data']);
    if(!self::$open) {
        die('<b>ERROR (/core/sql/1): Could not initialize database connection</b>');
    }

    self::$char = mysqli_set_charset(self::$open, $config['aF_sql_char']);
    if(!self::$char) {
        die('<br>ERROR (/core/sql/2): Could not set database charset</br>');
    }

    return self::$open;
}

public static function close() {
    self::$close = mysqli_close(self::$open);
    if(!self::$close) {
        die('<b>ERROR (/core/sql/3): Could not close database connection');
    }

    return TRUE;
}

mysqli_real_escape_string(aF_sql::$open, $_POST['username']);

就这样

class aF_sql {
public static $open;
public static $char;
public static $close;

public static function open() {
    global $config;

    self::$open = mysqli_connect($config['aF_sql_host'], $config['aF_sql_user'], $config['aF_sql_pass'], $config['aF_sql_data']);
    if(!self::$open) {
        die('<b>ERROR (/core/sql/1): Could not initialize database connection</b>');
    }

    self::$char = mysqli_set_charset(self::$open, $config['aF_sql_char']);
    if(!self::$char) {
        die('<br>ERROR (/core/sql/2): Could not set database charset</br>');
    }

    return self::$open;
}

public static function close() {
    self::$close = mysqli_close(self::$open);
    if(!self::$close) {
        die('<b>ERROR (/core/sql/3): Could not close database connection');
    }

    return TRUE;
}

mysqli_real_escape_string(aF_sql::$open, $_POST['username']);