php - 从另一个类获取已经创建的 mysqliDb 连接

Question

我有 MysqliDb https://github.com/joshcam/PHP-MySQLi-Database-Class .

在我的 php 类中:

<?php 
require_once ('MysqliDb.php');

class Main{

protected $db;   


public function __construct()
{
    $this->db = new MysqliDb ('localhost', 'root', 'tuncay', 'db');
}

}

Class A extends Main{

public function __construct()
{   
    $this->db = MysqliDb::getInstance();
    echo $this->db->where("id", 5)->getOne('test')['text'];
}

}

$a = new A();

?>

Fatal error: Call to a member function where() on null in /.../db/index.php on line 21 where() function belongs MysqliDb.php

怎么了？我从主类得到了 $this->db

我只想在A类中保留DB连接并使用它。

Answer 1

您的 A 类替换父类 __construct。尝试添加

Class A extends Main{
  public function __construct()
  {   
     parent::__construct();
     $this->db = MysqliDb::getInstance();
     echo $this->db->where("id", 5)->getOne('test')['text'];
  }
  ...
}