How to have children classes inherit MySQL Database connection in PHP

Question

I am using PHP 5.4.4 and I have a MySQL Database connection that I want to use for queries in the parent class and have that connection inherited by all children. I create a new instance of the parent and pass the db connection ($handler) as a parameter and the db connection becomes a property of the parent. When I create a new instance of a child I thought the db connection would be inherited as a property of the child, however I can only make that happen when I pass it is a parameter to both the child and parent:: constructor functions. This seems redundant to me and I am wondering what I am missing since I am new to PHP OOP.

require "pdo_connect.php"; //mysql db connection

class newUser {
    public $timestamp;
    public $dbconn;

    public function __construct($handler) { 
        $this->timestamp = time();
        $this->dbconn = $handler;
    }

    public function showdbconn() {
        //use $this->dbconn for mysql query
        print_r($this->dbconn);
    }
}

class social extends newUser {

    public function __construct($handler) {
        $this->message = 'message';
        parent::__construct($handler);
    }

    public function test() {
        //use $this->dbconn for mysql query
        print_r($this->dbconn);
    }
}

$x = new newUser($handler);
$x->showdbconn();  

$y = new social($handler); //why pass to child if passed to parent?
$y->test();

If you are creating two separate objects, one for parent and one for child then why would you expect them to share that in that hierarchy? When you create a `social` object and then construct `newUser` within it, then why create a separate `newUser` as well? — Hanky Panky, Aug 27 '14 at 17:45
This is an abbreviated example. The social object will be inheriting methods from the parent which I do not show here. — user2232681, Aug 27 '14 at 17:50
@user2232681 , you might find this useful: http://stackoverflow.com/a/11369679/727208 — tereško, Aug 27 '14 at 17:52

score 1 · Answer 1 · answered Aug 27 '14 at 17:50

Because $x is completely unrelated to $y. To see what I mean, look at this example:

$x = new newUser($handler);
$x->showdbconn();  

$z = new newUser($handler);
$z->showdbconn();

Since you have created two instances of newUser, you have to give the database connection to each one separately.

The same is true in your example. When you create a new social instance, it has to have the database connection passed to it the same way that every new newUser instance needs to have the database connection passed.

How to have children classes inherit MySQL Database connection in PHP

1 Answers1