Question

使用功能chief，我试图启动一个mysql连接，该连接将由多个类/函数全局使用。

当我将此类扩展到session类时，子类无法访问mysql对象$db。

class chief {

    protected $db;

    public function __construct() {

        $this->db=new stdClass();

        $this->db=new mysqli('', '', '', '');
    }

}

class session extends chief {
    public function __construct($address=null) {

        var_dump($this->db);
    }
}

打印结果：

chief Object
(
    [db:protected] => mysqli Object
        (
            [affected_rows] => 0
            [client_info] => mysqlnd 5.0.12-dev - 20150407 - $Id: 38fea24f2847fa7519001be390c98ae0acafe387 $
            [client_version] => 50012
            [connect_errno] => 0
            [connect_error] => 
            [errno] => 0
            [error] => 
            [error_list] => Array
                (
                )

            [field_count] => 0
            [host_info] => 127.0.0.1 via TCP/IP
            [info] => 
            [insert_id] => 0
            [server_info] => 5.5.60-MariaDB
            [server_version] => 50560
            [stat] => Uptime: 1845718  Threads: 2  Questions: 210730  Slow queries: 0  Opens: 587  Flush tables: 2  Open tables: 396  Queries per second avg: 0.114
            [sqlstate] => 00000
            [protocol_version] => 10
            [thread_id] => 6008
            [warning_count] => 0
        )

)

session Object
(
    [storage:session:private] => 
    [db:protected] => 
)

Answer 1

您需要在调用父构造函数之前

class session extends chief {
    public function __construct($address=null) {
        parent::__construct(); // <--- HERE
        var_dump($this->db);
    }
}

从文档中

注意：如果子类定义了构造函数，则不会隐式调用父构造函数。为了运行父构造函数，需要在子构造函数内调用parent :: __ construct（）。如果子级没有定义构造函数，则可以像常规的类方法一样从父类继承该子类（如果未声明为私有）。

http://php.net/manual/en/language.oop5.decon.php

PHP：子类无法访问MySQL对象

1 个答案: