Variables of extended class (PHP)

Question

I'm trying to extend a class with the variables in the constructor. Here a little example.

I have my index.php with the following code in it.

<?php

namespace System;

require_once 'App/Config.php';

spl_autoload_register(function($class) use ($config) {
  require_once $config['app']['root'] . '/' . $class . '.php';
});

$app = new App($config);
$app->Start();

?>

All is working fine. Now I in the constructor of the class App passed the config file.

<?php

namespace System;
use System\Librarys\Database;

class App
{
  protected $config;
  protected $connection;

  public function __construct($config)
  {
    $this->config     = $config;
    $this->connection = $this->getConnection();
  }

  public function getConnection()
  {
    $this->connection = new Database;
    $this->connection = $this->connection->Connect();

    return $this->connection;
  }

  public function Start()
  {
    echo 'test';
  }

  public function __destruct()
  {
    $this->config     = null;
    $this->connection = null;
  }
}

?>

Ok, all good! But now, I want to make the database connection. I extended the "App" class in the database class. Like below:

<?php

namespace System\Librarys;
use System\App;

class Database extends App
{
  public function __construct()
  {
    parent::__construct(??? HOW DO I GET THE VARIABLE FROM THE "APP" CLASS ???);

    var_dump($this->config);
  }
}

?>

And now, if I do a var_dump() on $this->config it returns null. That's clear because I didn't pass the $config var in the parent constructor. But how do I do that? I want to set all variables in the App class so I can extend it, and don't need to pass the variables to the other classes.

What im trying is to set all variables in the App class and then access it in the database class through the extended "App" class. — Sir Akaya
– Sir Akaya, Commented Sep 28, 2015 at 19:20
Ok, thats a detail. But how shoud i do that? is there a way to access the variables whitout passing it in every single class? i know static variables but thats not good practice they sad. — Sir Akaya
– Sir Akaya, Commented Sep 28, 2015 at 19:24

Timofey · Accepted Answer · 2015-09-28 19:32:26Z

1

It's not clear to me why you just doesn't use the same constructor on Database class. The code would be like this:

public function __construct($config)
{
   parent::__construct($config);
}

And then in App class

$this->connection = new Database($this->config);

By the way, if you're not going to add any more code to the Database constructor, you don't actually need it.

P.S. I see in your code bad class design. You're probably using the App class for global configuration and the database connection is a part of it. So you need to create a single class that would handle all database operations. Then you just use it in your App's instance. For instance:

class DB {
    function connect() { /* Some code */ }
    // More functions
}

class App {
    protected $db;
    // contructorts etc
    function run() {
        $this->db = new DB(/* some config */);
        // use it
    }
}

edited Sep 28, 2015 at 19:32

answered Sep 28, 2015 at 19:25

Timofey

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2 Comments

Sir Akaya Over a year ago

Yeah, i know this, but you know i have very much classes and passing the variables through every single class is hard, i mean is there a simple way to do that whitout static variables?

Timofey Over a year ago

see the edited answer. If you have a lot of classes and you have to pass some var throughout the whole structure — you have bad class design.

Zsw · Accepted Answer · 2015-09-28 19:33:45Z

0

When you call __construct() on Database, you can't get $this->config from App because it's not set yet.

You have to set the variable in the constructor before you can use it.

class Database extends App
{
    public function __construct()
    {
        parent::__construct("localhost");
        var_dump($this->config); // $this->config is now "localhost"
    }
}

answered Sep 28, 2015 at 19:33

Zsw

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