Referencing an extended class from inside the base class in PHP - php

Question

Sorry for perhaps not the most accurate title. I'm having trouble figuring out what this would even be called.
I'm somewhat new to OOP with php, as most of my time is spent with procedural programming. In an effort to better learn these concepts, I'm taking an existing application and rewriting portions of it using OOP. The below example is how I set up the base class, and then I extended the base class into several smaller classes for easier maintainability. Below, you can see how I extended the base class to create a user class. Please note, that my class definitions are in separate files, but I have a working autoloader that automatically registers them
class EventScheduler{
function __construct(){
// set up database connections here
}
}
class User extends EventScheduler{
private function getUserProfile($username){
// return an array here representing
// details of passed username from database
}
public function getUserType($username){
return $this->getUserProfile($username)['user_type'];
}
}
What I'd like to be able to do is reference the User class from inside the base class, like this:
$eventApp = new EventScheduler();
$userType = $eventApp->User->getUserProfile("nameHere");
What I'm currently doing is this:
$eventApp = new EventScheduler();
//do some stuff here using the base class
$users = new User();
$userType = $users->getUserProfile("nameHere");
But as I add more child classes, I don't want to have to instantiate every extended class like I did there, I'd like to have them all grouped under the base object, rather than having each extended class in it's own object.

Answer 1

What you want to do is
$users = new User();
//do some stuff here using the base class
// ie $users->someFunctionFromEventScheduler();
$userType = $users->getUserProfile("nameHere");

Answer 2

This is a good reason to start reading up on common design patterns in OOP. There are plenty of good resources for this online and a quick google search will yield plenty of results and examples mostly hosted on github.
The specific pattern I believe you are looking for is the mediator pattern (Mediator pattern example in PHP). Rather than extending a class, as you are doing in your example, the mediator pattern is useful when you want an instance of a class that has access to many other classes that can all communicate with each other through one base class. The premise is that 'One good friend is better than many acquaintances.`.
An example for you: (interfaces are incredibly useful here as they define specific characteristics that are required in each of the classes)
/**
* Interface Mediator
*/
interface Mediator {
/**
* #param string $key
* #param Mediated $mediated
* #return void
*/
public function attach($key, Mediated $mediated);
/**
* #param $key
* #return Mediated
*/
public function getAttached($key);
}
/**
* Interface Mediated
*/
interface Mediated {
/**
* #param Mediator $mediator
* #return void
*/
public function setMediator(Mediator $mediator);
/**
* #return Mediator
*/
public function getMediator();
}
Now we need a base mediator class, I'll use your event scheduler example. Notice that it implements the Mediator interface and must, as a result implement the methods the interface requires.
/**
* Class EventScheduler
*/
class EventScheduler implements Mediator {
/**
* A collection of mediated instances.
*
* #var array
*/
protected $mediated = [];
/**
* #param string $key
* #param Mediated $mediated
* #return void
*/
public function attach($key, Mediated $mediated)
{
// So upon attaching a mediated instance we can build the two
// way binding in one place using the key as the identifier.
// First we set $this on the mediated instance.
$mediated->setMediator($this);
// Then we add this instance to our mediated array inside this instance
$this->mediated[$key] = $mediated;
}
/**
* #param $key
* #return Mediated
*/
public function getAttached($key)
{
return $this->mediated[$key];
}
}
Now we can setup a mediated instance. That can be attached to the mediator. Notice it implements the Mediated interface.
/**
* Class User
*/
class User implements Mediated {
/**
* #var Mediator
*/
protected $mediator;
/**
* #param Mediator $mediator
* #return void
*/
public function setMediator(Mediator $mediator)
{
$this->mediator = $mediator;
}
/**
* #return Mediator
*/
public function getMediator()
{
return $this->mediator;
}
}
You can create as many of the mediated instances as you like and attach them to the Mediator instance. Bear in mind that this isn't a specific mediator, in that many instances can be attached, in most cases it's better to be explicit with which classes can be attached rather than allowing dynamic registration by a key.
$scheduler = new EventScheduler();
$user = new User();
$scheduler->attach('user', $user);
// Now we know that we can get the mediator from the User class
$user->getMediator();
// We can also get the User from the mediator itself.
$scheduler->getAttached('user');
As you attach more classes you'll notice that each of them can use their mediator to get instances of the other attached classes, this is where the concept of one good friend comes from.
This is just an example and not fully featured for brevity, but should give you a good idea why using common design patterns will help you enormously and is a very good place to start when learning OOP if you want to develop good habits.